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AMMIA
Master Analog Measurement Module
The AMMl A Analog Measurement Module combines three important Series 500 functions into a sin&e
module. First, the AMMlA functions as a standard analog input module, and will accept up to 16 sin-
gle-ended or eight differential analog input signals. It contains signal conditioning and switching cir-
cuitry for these channels. Second, the Ah&ilA selects and conditions analog signals from other analog
input modules in a Series 500 system. Last, the AMMlA serves as a IZbit A/D converter for its own
analog input channels, as well as any other analog signals which have been processed by the global se-
lect/conditioning circuitry. After analog conditioning, signals are routed to the A/D converter section
of the module for the analog-to-digital conversion process.
Input signals are applied to the AMMl A's analog input channels through on-card quick-connect screw
terminals. The AMMlA has a total of 16 local single-ended, or eight differential inputs. The input con-
figuration is controlled through software, rather than with hardware switches. These analog input
channels can be conditioned with programmable local gains of either xl or x10.
Global conditioning consists of a high-speed software-controlled gain amplifier with programmable xl,
x2, x5 and x10 gain values. All analog inputs connected to the Series 500 pass through the global circuit-
ry, whether the signals originate on the AMMlA or some other analog input module. Therefore, these
gain values can be applied to any analog input in the system.
For A/D conversion, the AMMlA uses a E-bit successive approximation converter. A maximum con-
version time of only l@ec allows sampling rates as high as 62.5kI-L~. to maximize resolution, the
AMMlA has 0-IOV and +lOV A/D converter ranges which are software selectable.
CAUTION: Always turn off the system power before installing or removing modules. To minimize
the possibility of EMI radiation, always operate the system with the top cover in place and properly
secured.
The AMMlA is designed to be used only in slot 1 of the 500-series chassis, Model 575, or Model 576. To
install the module in a series 500 chassis, first remove the baseboard top cover and install the module
in slot 1 with the component side facing the power supply. For Model 575 or 576, please refer to the Set-
up section of its hardware manual.
Document Number: 501-913-01 Rev. B
AMMl A-l
TPB TPl3 TPl2TP4 TPlO '61
go 0
*O
0
q
0
0
0
0
0
0
~0
0
0
0
0
0
0
i
SOFTWARE CONSIDERATIONS THE AMMlA ANALOG MODULE
The AhJMlA module, when used in a 575 or 500 series chassis, operates with KDAC500 and a variety
of 3rd party software packages. For programmers who are writing their own register level driver, the
following data format explanation is provided:
BASIC PEEK/POKE operations and equivalent commands in other programming languages must ac-
cess the AMMIA as a 16-bit A/D module, rather than a 12-bit module. The AMMlA's 12-bit resolution
results from padding the last four of the 16 bits with zeros. The least significant bit position where
change will be observed in the fifth least significant bit, and the low byte will increment by 1000 binary.
The high and low bytes carry information as follows:
high byte low byte
1i
HHHHHHHH LLLL 0000
where: H = high-order bit (8)
L = low-order bit (4)
0 = bit permanently wired low (4)
Thus, a complete read of the AMMlA requires that a high and low byte be read. Converting the high
and low bytes to a full A/D count can be performed as follows:
RES = (256 * HIBYTE) + LOWBYTE
The equivalent voltage can be calculated by multiplying RES by the bit value for a 16-bit conversion
referenced to the A/D converter range. Consult the following examples:
Assume a decimal value for HIBYTE of 170, and 48 for LOWBYTE. RES can be calculated as:
RES = 170956 i- 48
RES = 43568
1. For an A/D range of +lO volts, calculate the corresponding voltage reading as:
V = (RES X.20/65536) - 10
V = (43568 + 20/65536) -10
V = 3.296V
2. For an A/D range of O-10 volts, calculate the corresponding voltage reading as:
v = (RES + 10/65536)
V = (43568 * 10/65536)
V=6.648
AM-MA-3
AMMI A High-speed Acquisition Mode with the ANINQ Command (KDACXOO)
The ANINQ command can operate the Ah4hJlA module in a high-speed "auto-acquire" mode at an ag-
gregated throughput rate of up to 62.5kI-I~. Auto-acquire applies to single or multiple channels. For
multiple channels, the per-channel scan rate equals 62.5lcJ& divided by the number of channels.
The analog input modules AIM2 and AlM3A can also provide up to 62.5kHz throughput when these
modules are used in a system containing an AMMIA.
To operate the AMMlA in auto-acquire mode, you must satisfy the following requirements:
1. The analog input channels sampled by ANINQ must be on an AMMlA, AIM& or AIM3A.
2. All channels sampled by the specific ANINQ command must be on one module.
3. The AMMlA's input filter must be set to 1001612.
If any of these conditions cannot be met, the speed of an ANINQ command will revert to the speed of
a BGREAD command. Under these circumstances, it is better to use BGREAD in order to take advan-
tage of foreground/background operating mode.
NOTE: The ANlNQ command in KDAC500 has been optimized for auto-acquire operation with the
AMMIA. If you attempt auto-acquire mode with BASIC's PEEK/POKE, or the memory READ/WRITE
commands of other languages, you may receive incorrect data. If you do not use KDAC500, Keithley
suggests that you run the AMMlA only in "regular acquisition mode". This mode is described under
the heading "SELECT ACQUISlTION MODE" later in this manual.
Self-calibrating During "CALL KDINIT" (KDACSOO)
The AMMlA module performs a calibration of the A/D gain and range each time KDINlT is called.
KDAC500 executes the KDlNlT function automatically each time it is loaded. KDAC500 will expect an
Ah4MlA module in the system if the configuration file (CONFIG.TBL) shows an AMMlA in slot 1. If
the software cannot complete the calibration, it will issue an error message such as "Unable to calibrate
A/D module". If this occurs, check that:
1. The data acquisition hardware is turned on.
2. The cable between the hardware and the host computer is connected.
3. An AMMlA module is mounted in slot 1 of the data acquisition system
AMMlA-4
Connection and Operation
Signal Connection
The Ah4MlA can be programmed for either differential or single-ended local input configurations.
These local input signals are applied to screw terminals located toward the rear portion of the AMMIA.
Single-ended and differential inputs use the same screw terminals.
The channel numbers are shown in Figure 1. Figure 2 shows typical connections for channels 0 through
7 in differential mode. For differential mode, connect the high (-I-) side of an input signal to the (+> ter-
minal, and the low (-> side of the signal to the corresponding (-) terminal. When the AMMlA is config-
ured for single-ended input, conzlect the high (+) side of the input signal to one of the terminals 0
through 15, and the low (-1 side to the module ground at either end of the terminal strip. In Figure 2, the
numbers listed in parentheses above the lower connector are the single-ended local channels 9 through
15.
Measured
Voltage
Series 500
Chassis Ground
Figure 2 Typical Differential Connection (Channel 0 Shown)
AMMlA-5
CAUTION: The AMMlA inputs are non-isolated. In single-ended mode, one side of the input is
connected to power line ground. Any signal connected to the AMMlA must also be referenced to
power line ground, or module or system damage may occur Also note that inaccuracies on other
channels may result. When used in differential mode, the AMMlA local inputs must both be within
HOV of module ground for proper operation. If either signal exceeds k3OV module damage may re-
sult.
In many situations, shielded cable may be required to minimize EMI radiation, or to keep noise to a
minimum. If shielded cable is used, connect the shield to ground only, and do not use the shield as a
signal-carrying lead. Usually, a module ground terminal should be used, but in some cases better re-
sults may be obtained by using one of the baseboard ground posts. Use the configuration that results in
the lowest noise.
For shielding to be effective, the shield must contain both high and low signal wires, and must not carry
any other signals. If a number of AMMlA signal input lines are shielded, all shields should be connect-
ed to the same ground terminal.
Signal Conditioning
Figure 3 shows a simplified block diagram of the MIA. The module is divided into six general sec-
tions: a local multiplexer, a local programmable gain amplifier, a global multiplexer, a global program-
mable gain amplifier, a programmable low-pass filter, and a 12-hit A/D converter.
Local input signals from channels 0 to 15 are applied to the local multiplexer for selection. At any given
time, only one channel will be selected, as determined by the SELECT CHANNEL command (covered
later in this section). The signal from the selected channel is then routed through a local programmable
gain amplifier to the global multiplexer for further signal selection and conditioning.
The global multiplexer selects a single signal from among the 10 slots in the 500 series chassis. In this
manner, signals from any of the 10 slots can be selected by software. The global multiplexer is controlled
by the SELECT SLOT command, discussed later in this section. Users of the 575 or 576 should consult
its hardware manual for information on how the global multiplexer selects signals from slot 3 and from
the 3B channel connector.
After the signal is selected, the Global PGA applies softwareselectable gains of xl, x2, x5, or x10. The
signal finally passes through a one-pole filter with software selectable -3db frequencies of either lOOkI&
or 2kH.z. When this signal conditioning process is complete, the signal is routed to the 12-bit A/D con-
verter for digitization. After the conversion process, digital data representing the applied signal travels
via the baseboard and interface card to the host computer.
AMMlA-6
Local
Prcgrammable
Gain Amplifiir
16 Single-ended or
Gr--l DC1orX10) Global
Programmable
ti
8 Differential LOCAL Gain Amplifier
Inputs MUX (Xl .X2.X5.OR
(input Mode
-
Programmably
Selected) 12BlT =
GLOW iL
MUX AID AND =
LQ S/H Z
Analog Inputs f
Programmable
Lccal
Channel
From Other
Slots ~ J Programnable
Filter
Selection (1ookHz OR
2kHz)
Figure 3. AMMlA Signal Conditioning
Input Filtering
Noise introduced into the input signal can corrupt the accuracy of the measurement. Such noise will
usually be seen as an unsteady reading, or, in some cases, as a constant offset. In the former case, the
effects of noise will usually be quite obvious, but may not be noticeable in the steady-state offset situa-
tion.
Frequently, noise is introduced into the signal from 50 to 6OHz power sources. In many cases, noise can
be attenuated by shielding or relocating the input signal lines, as discussed earlier. It may also be pos-
sible to reject unwanted 6OHz noise by using the AMMlA in differential mode. Since the 60Hz noise
may also be present on the low side of the signal, the differential amplifier will reject the common sig-
nal. In more difficult situations, however, it may be necessary to filter the input signal to achieve the
necessary noise reduction.
When noise is a problem, a single-pole low-pass filter like the one shown in Figure 4 can be connected
between the input signal and the corresponding AMMlA channel. Note that the filter is made up of a
single capacitor and resistor with the capacitor connected between the AMMlA channel input termi-
nals and the module ground terminal. The resistor is then placed in series with the high input signal
lead.
From Signal C- To AMMIA Input
--r
I
l
Figure 4. Input Filtering
AMMlA-7
A common reference point for a simple filter like the one in Figure 4 is the -3dB or half-power point,
which is given as follows:
fsMB= 1/(27cRC)
where f is in Hz, C is in farads, R is in ohms. Above this frequency filter response will roll off (decrease)
at a rate of -2OdB per decade. Thus, each time the frequency increases by a factor of 10, filter output volt-
age decreases by a factor of 10 (-20dB).
Although such filtering can quiet down a noisy signal, there is a tradeoff in the form of slower re-
sponse. This response time may be important in the case of a rapidly changing input signal. For the filter
in Figure 4, the response time to 1% of fmal value is 4.6RC, while the response times to 0.1% and 0.01%
of final value are 6.9RC and 9.2RC, respectively.
As a example, assume that 10 counts of 6OHz noise is present in the input signal. To reduce the noise to
one count, an attenuation factor of 10 (-20dB) at 6OHz wiIl be necessary. Thus, the filter should have a -
3dB point of 6OHz.
To determine the relative RC values, the above equations can be rearranged to solve for either R or C.
If we wish to choose a nominal capacitor value and then solve for the resistance, we have:
R = 1/(2rrCf,,)
Choosing a nominal value of 2@ for C, the necessary resistance is:
R=1/(2xx(2xW)x6Hz)
R = 13.263k
The resulting response times with these R and C values would be:
t(l%) = 4.6RC = 122ms
t(O.l%) = 6.9RC = 183ms
t(O.O1%) = 9.2RC = 244ms
Note that there are a number of RC values that can be used in a given situation. To minimize the effects
of the series resistance, however, it s recommended that the value of R be kept under 2OwZ.
Current-to-Voltage Conversion
AMMlA local inputs are designed to accept voltages in the range of +lOV. Thus, the AMh41A can be
directly connected to many signal sources. Some transducers and instrumentation, however, provide
current outputs that must be converted into voltages in order to be measured through an AMMl Ainput
channel.
AMMA-
When connecting current inputs to the AM&$1 A, a resistor should be installed across the input to make
the necessary current-to-voltage conversion. J4, J5, and J6 provide locations for installing these resistors
on the AMMlA. Refer to the circuit schematic and board layout diagrams for header information.
The value of the resistor can be determined from Ohm's Law as follows:
R=E/I
Where R is the resistance in ohms, E is the maximum desired voltage in volts (usually the upper range
limit of the A/D converter), and I is the maximum anticipated current in amps.
As an example, assume the A/D converter range is zero to +lOV and that the expected current lies in
the range of four to 4OmA. The required resistance is:
R = 10/0.04
R=250
Thus, a 25OQ resistor should be installed across the input of the channel in question (note that a 25OQ
value is required when using KDAC500 engineering units conversion). Since current measurement ac-
curacy is directly related to the accuracy of the resistor, use the smallest tolerance resistor available (typ-
ically 0.1%). Suitable 25OQ precision resistors can be purchased from Dale Resistors, (P/N
RN55E2500B), or from Keithley (P/N 500~RES-250).
Analog-to-Digital Converter Timing
When programmin g high-speed sampling sequences, certain timing constraints concerning the A/D
conversion cycle should be observed. Depending on the AMMlA's acquire mode, the scenario for re-
ceiving converted values from the A/D is very different. Refer to the discussion of the acquire modes
below for specific instruction on how to process analog signals.
To increase system throughput, data latches have been provided on the AMMl A, making data from the
last conversion available while the converter is busy processing another reading. The data is refreshed
(updated) every time a conversion has been completed.
External Trigger Operation.
The AMMlA has the capability of triggering an acquisition from an external TI'L-level source. The
jumper on the AMMlA 03) dictates the triggering source. The external trigger can only be used in
62.5kHz auto acquire mode which is explained below in the SET ACQUISITION MODE command dis-
cussion.
When the AMMlA is in 62.5161~ auto acquire mode, the trigger source can be set to either external or
internal by the J3 jumper. When set for internal triggering, the AMMlA continuously converts analog
signals as described below in the SET ACQUISITION MODE command discussion. When the J3 jumper
is removed, a TTL-level gating signal can be attached to pin 2 of the jumper header. A low level applied
to pin 2 will enable the continuous conversion process, a high level applied to pin 2 will suspend the
AMMlA-9
continuous conversion process. In either case, the application program must synchronize itself to the
conversion process by polling the conversion status as explained in the SELECT ACQUISlTION MODE
command discussion.
The pm configuration of the jumper header is as follows:
pill1 Special trigger output - valid only when using TRGl
pm2 trigger input
pm3 OV (ground) - for internal triggering
The J3 jumper should be across pins 2 and 3 for internal trigger operation. The jumper should be re
moved and the external gating source should be connected to pin 2 for external gate operation. The J3
jumper should be across pins 1 and 2 if a TRGl analog trigger module is being utilized.
Commands
Table 1 summa rizes the commands used with the AMMlA. Note that several commands share the
CMDA and CMDB locations. Some commands use only selected bits in the command byte, others are
differentiated by whether a read or write operation is performed.
Table 1. Commands Used with the A.&M&l
5001575
Command Address Signal Line Bits Used
SELECT CHANNEL xxx80 CMDA (Write) DO-D3
SELECT LOCAL CHANNEL MODE XX&O CMDA (Write) D4
SELECT LOCAL GAIN CMDA (Write) D5
SELECT ACQUISITION MODE XXX80 CMDA (Write) D6
SELECT HLTER xxx80 CMDA (Write) D7
SELECT SLOT xxx81 CMDB (Write) DO-D3
SELECT CMDA READ MODE xxx81 CMDB (Write) lx
SELECT RANGE xxx81 CMDB (Write) D5
SELECT GLOBAL GAIN xxx81 CMDB (Write) D6-D7
RESET AND RECAL xxx9A CMDC (Write) ALL
A/D LOW DATA* XXX80 CMDA (Read) ALL
A/D STATUS XXX80 CMDA (Read) ALL
A/D HIGH DATA xxx81 CMDB (Read) ALL
A/D START xxx9B CMDD (Write) ALL
EOC (end-of-conversion) STATUS xX&B CMDD (Read) ALL
The information read from CMDA is selected by the SELECT Ch4DA READ MODE command. Refer to the sections
below for the full description of their operations.
The "xxx" in the 500/575 address column sign&s the three hexadecimal digits that make up the base
hardware address which is either switch selected or programmed on the IBIN-A or IBIN-F'S/2 interface
card. The suggested address is &HCFF80, so "xxx" = "&HCFl?`.
AMMIA-10
Select Channel, Local Gain, Filter, Acquisition Mode, and Channel Mode.
D71D6ID5lD4031D2IDlIDO
I
) 4 4 4- V
t- Channel Select: SE (O-15), DIFF (O-7)
Channel Mode: Single-ended (l), DIFF (0)
Local Gain: Xl (0), Xl 0 (1)
/ ACQ Mode: 62.5kHz Auto Acquire (I), Regular Acquire (0)
Filter Mode: 1OOkHz (0), 2kHz (1)
Figure 5. CMDA Write Format
Select Slot, Range, Global Gain, and CMDA Read Mode.
D71D6 ID51 D41D3 1021 DllDO Byte Format
CMDA Read Mode: A/D Status (0), Low Data (1)
Select Range: -1OVfl OV(l), 0 fl OV(0)
Select Global Gain: Xl (0), X2 (l), X5 (2), X10 (3)
Figure 6. CMDB Write Format
SELECT CHANNEL
Location: xxx80
The SELECT CHANNE L command is used to control the local signal multiplexer on the AMMl A, thus
determining which of the local input channels is selected for A/D conversion. This command affects
only those signals connected to the AMMlA local inputs, and does not affect input channels connected
to modules located in other slots. SELECT CHANNE L must be used in conjunction with the SELECT
SLOT command to select the channels on the AMMlA to be measured.
Note that the channel number occupies the least significant four bits of CMDA. Make sure that the chan-
nel number is combined with the appropriate upper four bits, as shown in Figure 5, before it is sent.
AMMIA-11
SELECT LOCAL CHANNEL MODE
Location: xxx80
The SELECT LOCAL CHAbINE L MODE command controls the configuration of the local input chan-
nels on the AMMl A. The AMMlA input channels can be configured as either 16 singleended or eight
differential input channels. This command is selected by assigning a value to the D4 position of CMDA
as shown in Figure 5. A value of 1 will set the inputs to singleended, a value of 0 will set them to dif-
ferential.
Make sure that the other bits in the CMDA byte represent the desired selections before it is sent.
SELECT LOCAL GAIN
Location: xxx80
The gain applied to the local channels of the AMMlA is programmable and can be set by assigning a
value to bit position D5 in CMDA. As shown in Figure 5, a value of 0 will apply a local gain of Xl and
a value of 1 will apply a local gain of Xl0 to the AMMlA input channels.
The local gain can be changed at any time as long as the channel settling time is satisfied before the con-
version is started.
Make sure that the other bits in the CMDA byte represent the desired selections before it is sent.
SELECT ACQUISITION MODE
Location: xxx80
The AMMlA has the capability of operating in either of two modes; the regular acquisition mode, and
the 62.5kHz auto acquisition mode. As shown in Figure 5, the acquisition mode is set by assigning a
value to bit position D6 in CMDA. Assigning a value of 0 enables regular acquisition mode, a value of
1 enables 62.5kHz auto acquisition mode.
To acquire an analog reading when in the regular acquisition mode, the slot, channel, and gain must be
selected. Then, after the appropriate settling time, the AMMlA is issued a START CONVERSION com-
mand. At this time, the AMMlA latches the signal and starts the digitization process. The EOC STATUS
command can be polled for end-of-conversion (EOC) after which the digitized value can be read. The
conversion process will consume approximately 16usec.
Since the incoming signal is latched when the START CONVERSION command is issued, the slot, chan-
nel, and gain selections can be changed immediately after the command is issued. This will allow the
settling time for the new selections to be satisfied concurrently with the conversion of the previous se-
lection. This type of operation is not required but will increase the throughput capability of regular ac-
quisition mode.
Ah4MlA-12
The auto acquisition mode allows full 62.5kHz'acquisition speed on analog signals. Upon placing the
AMMlA in this mode, the A/D enters a freerunnin g 62.5kHz conversion process. Do not attempt to
issue the START CONVERSION command in this mode.
Some microcomputers may not be capable of keeping up with the AMMlA in auto acquire mode. If the
AMMlA outpaces your microcomputer, the data points will be unreliable.
After the completion of a conversion, the AMMlA begins the next conversion immediately The EOC
STATUS command can be used to synchronize your program with the conversions. The conversions
will take place on the slot and channel that are presently selected at a rate of 62.5kHz. The conversion
status bit will be reset by the reading of either the high or low A/D data bytes. Figure 7 shows the timing
for single channel auto acquire operation.
Read High I 1
Byte
Completed
Figure 7. Single Channel Auto Acquire Timing
While in auto acquire mode, the EOC status bit will become true (low) after the first A/D conversion.
Even though the next conversion begins immediately, the status bit remains true until the A/D data is
read. If the data is not read, it is overwritten.
Figure 8 shows a example of the EOC status being polled only after one or more conversions have taken
place. Even though the EOC status bit indicates that the conversion is complete, there is no way of tell-
ing if another conversion is about to be completed. Trying to read the data while the latches are being
updated will cause unreliable results- To guarantee reliable readings, your program should synchronize
itself with the AMMlA by taking a dummy reading to clear the conversion status bit. The next time the
status bit indicates the end of a conversion, the data at the A/D latch will be valid for the full 16usec.
For multichannel auto acquisition operation, all of the settling times for the new channel must be satis-
fied 4pec before the EOC takes place. If it is not settled, it may be necessary to throw away a reading
or two until it has settled. To maxim&z e the available settling time, it is recommended that slot selection,
gain selection, and channel selection take place directly after the EOC becomes true.
AMMlA-13
1 St 2nd 3rd
Conversion Conversion Conversion
EOC Status -f k
Bit (CMDD) ,/
I I I
I t
Poll EOC : b \
Bit Status (CMDD) , Data in the ND
I ,
I I
Latch is Updated Here. b
\
Although the converter status indicates The EOC status bit
a completed conversion here, reading the data remains low until the
might be coicident with an update of the High or Low data are read.
data from the converter.
Figure 8. PoIling the Status Bit After One or More Conversions
For optimum operation follow these steps:
1. Monitor the EOC status bit until an end-of-conversion is sensed.
2. Select a new gain, a new slot, and a new channel, as needed.
3. Read the latched data from the last conversion.
A timing diagram for multichannel operation is shown in Figure 9.
EOC Status
Bit (CMDD) J I
1
I
Poll EOC 1
BitStetus(CMDD) . , f-f 1
1
Gain
Select
settling time] ! 7
Slot
Select
Channel
Select
Read Low
Byte
Read High
Byte
I for Chekel
B
f1 \
\
for Chektel
C
\'
Read
Chdnel Read cilarlnel CflZl~l
A Date Ready Channel B Date Ready B
A
Figure 9. Multichannel Operation in Auto Acquire Mode
AMMlA-14
Even though the AMMlA is capable of digitizing analog signals at 62.5kHz, some modules in the Series
500 module library are not capable of settling at these speeds. When doing multichannel acquisition,
consult the individual module's hardware manual for appropriate settling times.
SELECT FILTER
Location: ~xx80
Two filters are available in the AMMIA; a 1OOkHz filter, and a 2kHz filter. These filters restrict the band-
width of the incoming signal, rejecting either noise or unwanted high frequency components that may
create aliasing.
It is desirable to reject all signal frequency components that are greater than l/2 the sampling frequency.
These frequency components cause aliasing which produces inaccurate waveform representation. The
filters are designed to reject frequencies above 1OOkHz or above 2kHz, depending on the filter used. The
1OOkHz filter, while not providing complete protection against aliasing, does reduce the system noise
with a minimal effect on settling time.
Assign a value of 0 to bit position D7 in CMDA to select the 1OOkHz filter, assign a value of 1 to select
the 2kHz filter.
Make sure that the other bits in the CMDA byte represent the desired selection before it is sent.
SELECT SLOT
Location: xxx81
The SELECT SLOT command controls the global multiplexer on the AMMl A, selecting the appropriate
slot on the Series 500 baseboard from which to read the input.
The value to be written to the SELECT SLOT location occupies the four least significant binary digits of
the command. Make sure that the slot number is combined with the appropriate upper four bits as
shown in Figure 6 before it is sent.
As indicated in Table 2, there are other values besides slot numbers that can be written to this location.
These values select ground, +5V, and +lOV sources and are intended primarily for diagnostic purposes.
AMMlA-15
Table 2. Values Written to the SELECT SLOT Location
Function Binary
Ground (0 volts) bbbbOOO0
Slot 1 bbbwoO1
Slot 2 bbbbOOl0
Slot 3 bbbbOOl1
Slot 4 bbbbOlO0
Slot 5 bbbbOlO1
Slot 6 bbbbO110
Slot 7 bbbbOll1
Slot 8 bbbblOO0
Slot 9 bbbblOO1
Slot 10 bbbblOl0
Reserved bbbbloll
Reserved bbbbllO0
+lOV Reference bbbbllol
Ground (0 volts) bbbblll0
+5V Digital Power Supply bbbbllll
SELECT CMTIA READ MODE
Location: xxx81
This command selects the usage of the CMDA read. Two types of information can be read from CMDA
(note that this affects only the read operation of CMDA), these are, the low data byte of the A/D or the
A/D status. In the low data byte mode, CMDA supplies the low byte of the A/D readings. In the A/D
status mode, CMDA supplies status directly from the A/D. The A/D status is described further in the
sections below.
NOTE: When the CMDA read mode is set to A/D status, a reset and recal sequence will be initiated by
any start conversion comman d. The start conversion command can come either from a write to CMDD,
or from the auto acquire mode hardware if this mode has been enabled by a value of 1 in bit position
D6 of CMDA. To avoid accidentally initiating a reset and recal sequence, be sure bit position D6 of
CMDA is set to a value of 0 before changing the CMDA read mode to A/D status. Do not write to
CMDD or change D6 of CMDA to a value of 1 as long as the CMDA read mode is set to A/D status.
Assign a value of 0 to bit position D4 in CMDB to read A/D status from CMDA, assign it a value of 1
to read the A/D low data byte.
Make sure that the bit is combined with the other appropriate bits as shown in Figure 6 before it is sent.
AMMlA-16
SELECT RANGE
Location: xxx81
The AMMIA has two programmable ranges; +lOV (bipolar 1OV) and zero to +lOV (unipolar 1OV). As-
signing a value of 0 to bit position D5 in CMDB will select the AMMlA unipolar 1OV range, assigning
a value of 1 will select the bipolar 1OV range.
Make sure that this bit is combined with the other appropriate bits as shown in Figure 6 before it is sent.
SELECT GLOBAL GAIN
Location: xxx81
The GLOBAL GAIN command controls the PGA Wrogrammable Gain Amplifier) located on the
AMMIA module. Since all analog inputs are processed by the PGA, the GLOBAL GAIN command af-
fects every analog input connected to the Series 500. This command is issued in combination with other
commands on CMDB. The GLOBAL GAIN value occupies the two most significant bits of CMDB and
must be combined with the other bits of the CMDB byte before it is issued.
Four programmable gain values, xl, x2, x5, and x10, are available with the PGA. These gains are select-
ed by setting the appropriate bits in CMDB before it is issued.
Table 3. Values Written to the GLOBAL GAIN Location
PGA Gain BiIla.ly
Xl OObbbbbb
x2 01 bbbbbb
x5 1Obbbbbb
x10 llbbbbbb
RESET AND RECAL
Location: xxx9A
The RESET AND RECAL command starts the internal A/D calibration process. The process takes ap-
proximately 36Omsec and should be completed once every time the system is powered up.
After issuing this command, wait at least 360msec before any conversions are attempted. To make sure
that the calibration has taken place, set the CMDA read-mode to A/D status, as described above. The
bit configuration of the calibration status is described below. This bit can be polled to make sure cali-
bration has been completed.
This command has no specific data associated with it, any value sent will start the calibration process.
AMMlA-17
AfD LOW DATA-A/D STATUS
Location: xxx80
The contents of CMDA depends on the state of the AMMlA set by the SELECT CMDA READ MODE
command. If D4 of CMDB has been set to 0, CMDA returns the A/D status of the AMMIA. If D4 has
been set to 1, the low byte of the A/D counts is returned in CMDA.
When AMMlA is in the A/D status mode, the bit configuration of the CMDA byte is as follows:
Do none
Dl none
D2 none
D3 none
D4 none
D5 TRACKING (1=tracking in process, O=tracking stopped)
D6 CONVERTING (l=conversion in process, O=no conversion in process)
D7 CALIBRATING (l=calibration in process, O=calibration not in process)
After the A/D completes a digitization of an analog signal, it begins a process called tracking. The
A/D consumes 4l.~x for the analog signal at its input to be tracked to the specified accuracy. The time
relationship between the TRACKlNG bit and the EOC bit in CMDD is shown in Figure 10.
The converting bit indicates the actual A/D conversion status. The time relationship between the
CONVERTING bit and the EOC bit in CMDD is shown in Figure 10.
Won1 Reset Until
Data is Read
EOC Bit
in CMDD F 16~s
I
I
Tracking Bit I
in CMDA I
t
Converting Bit
in CMDA `U Conversion
Begins
Figure 10. Time Relationship of Status Bits
The CALIBRATING bit returns the status of a RESET AND RECAL command as described above.
If the AMMlA is in the low data mode, the byte received is the low byte of a 16 bit A/D conversion.
However, the 4 least significant bits will be set to 0, thereby providing 12-bit resolution effectively Since
the module incorporates data latches, one conversion may be read while another conversion is in
AMMIA-18
progress. To find out when data from one conversion is available, use the A/D START/EOC STATUS
command, discussed below.
Reading this location resets the EOC status.
ND HIGH DATA
Location: xxx81
The A/D HIGH DATA command performs essentially the same function as the A/D LOW DATA com-
mand, except that the high data byte is returned. Since the AMMlA's 12-bit resolution is actually the
resuh of setting the four least significant bits of a l&bit conversion to 0, all of the bits in the high data
byte of an AMMlA are sign&ant.
Once both the low and the high data bytes have been obtained, the total number of counts representing
A/D converter data can be determined using the following formula:
CO = DL + 256*DH
CO represents the number of counts, and DL and DH are the low and high bytes respectively. With the
AMMlA, the number of counts will lie in the range of 0 to 65,535 minus 4 least significant bit's worth,
or 0 to 65520.
Reading this location resets the EOC status.
A/D START
Location: xxx9B
The A/D START COMMAND starts the A/D conversion process. Writing to the A/D START location
will trigger (start) the A/D conversion cycle. Although any value (O-255) can be written to trigger a con-
version, a value of 255 should be used to minimize noise. Do not issue an A/D start command while in
auto acquisition mode or the internal tuning of the A/D will be skewed.
The A/D conversion cycle takes approximately 16pec. During this period, the converter should not be
m-triggered. Status of the conversion process can be checked by accessing the EOC STATUS command.
EOC STATUS
Location: xxx9B
The EOC STATUS command returns a byte of data which indicates the state of the conversion process.
The returned value will depend on whether a conversion has been completed (see Table 4).
AMMlA-19
Table 4. Values Read from the AID START/STATUS Location
EOC Status Bi.tlaly
Conversion in process lxxxxxxx
End-of-conversion OXXXXXXX
Calibration
This section contains calibration procedures for the AMMlA module. The procedures include pro-
grams which have been written with BASIC's PEEK and POKE commands for use on a Series 500 or
575. Note that these procedures are intended for the field and may not be as accurate as those used in
the factory. If you are not familiar with calibration equipment, do not attempt AMMlA calibration.
This procedure presumes that the unit is in working condition and at least one factory calibration has
been done in the past. An additional procedure is necessary to select R2.5, R26, R27 and R28 if the volt-
age reference U13 has been replaced. The procedure for replacing U13 is described after the section on
troubleshooting.
Environmental Conditions
Calibration should be performed at an ambient temperature of 23'C (f5"). Turn on the system power
and allow it to warm up for at least 10 minutes before beginning the calibration procedure.
Recommended Calibration Equipment
The following equipment is recommended for AMMlA calibration. Other equipment may be used as
long as the corresponding specifications are at least as good as those given below.
1. Keithley Model 196 DMM (0.005% basic DC accuracy).
Key specs needed on DMM:
DC accuracy of 60 ppm on a 1OV reading.
Sufficient resolution to read one microvolt offsets.
2. EDC Model ElOOC Millivolt Reference Source (0.005% accuracy).
Key specs needed on source:
Provides an output between 0.5 and 0.99 vohs.
Maintains its output stable to 10 ppm for five minutes.
Ovetiew of Adjustment Sequence
1. Adjust IOV reference.
2. Adjust 4V reference.
3. Adjust Global Amp offset.
4. Adjust attenuator offset.
5. Adjust both Local amp offsets.
6. Adjust Local amp Xl0 gain.
7. Tweak A/D gain with 4V reference adjustment.
AMMI A-20
Calibration Procedure
The test points, potentiometers, and connectors referenced in the procedure are shown in Figure 1.
Adjust 1OV reference
1. Connect the DMM high lead to TP7 (1OV). Connect the DMM low lead to TP4 (AGND). Select DCV
and autoranging.
2. Adjust pot R7 for lO.OCQOvolts +lOOj.tV.
Adjust 4V reference
The following procedure will bring the 4V reference within range so that it can be calibrated accurately
later.
1. Connect the DMM high lead to TP8 (4V). Connect the DMM low lead to TP4 (AGND). Select DCV
and autoranging.
2. Adjust pot R8 for 4.000 volts +lmV. This adjustment will be tweaked later.
Adjust Global Amp offset
1. Connect the DMM high lead to TP9. Connect the DMM low lead to TP4 (AGND). Select DCV and
autoranging.
2. Select the PGA gain of X10 and the zero voltage reference input by POKEing a value of 192 to
CMDB of slot 1 and a value of 0 to CMDA of slot 1.
3. Adjust pot R9 for zero volts +10j~V.
Adjust attenuator offset
1. Select the Xl global gain and the zero voltage reference input by POKEing a value of zero to both
CMBA and Ch4DB of slot 1.
2. Connect the DMM high lead to TPlO. Connect the DMM low level to TP9. Select DCV autoranging.
3. Adjust pot RlO for zero volts +10j.~V.
Adjust both Local amp offsets
1. Connect a short jumper wire between differential channel 0 high input and signal common (termi-
nals 9 and 10 on Jl). Connect a short jumper wire between differential channel 0 low input and sig-
nal common (terminals 1 and 2 on J2).
2. Connect the DMM high lead to TP3. Connect the DMM low lead to TP4. Select DCV and autorang-
ing.
3. Select differential input and Xl gain by POKEing a value of 0 to CODA of slot 1.
4. Record the DMM reading as Vout(l) for use later.
5. Select a gain of X10 by POKEing a value of 32 to CMDA of slot 1.
6. Record the DMM reading as Vout(2).
7. Compute the offset contribution of U6 as follows: V, = (lO*Vo,(l) - V,(2))/9.
8. Adjust pot R5 so that the DMM reads the voltage computed for V,.
AMMl A-21
9. Select the Xl gain again by POKEing a value of zero to CMDA of slot 1.
10. Adjust pot R6 for a DMM reading of zero volts +lOpV If desired, the adjustment can be
checked by once again outputting data: CMDA = 32. The DMM should read zero volts
k1OO~V
Adjust Local amp X10 gain
1. Remove the jumper between terminals 9 and 10 of Jl that was installed in previous step.
Connect voltage source (+) output to terminal 9 of Jl, and the voltage source (-) output to
terminal 10 of Jl. Leave the jumper installed between terminals 1 and 2 of J2.
2. Connect the high lead of the DMM to TP3. Connect the low lead of the DMM to TP4. Select
DCV and autoranging.
3. Set the voltage source to a value of 0.99 volts.
4. Select the X10 gain by POKEing a value of 32 to CMDA of slot 1.
5. Adjust pot R4 for a reading of 9.9 volts.
Tweak A/D gain with 4V reference adjustment
1. Use the test setup from the previous step. The DMM should be reading a voltage of approx-
imately 9.9 volts on TP3.
2. Select channel 0, local gain of X10, differential input, filter on QkHz), slot 1, unipolar 1OV
range, and global gain of Xl by POKEing values of 160 and 17 to CMDA and CMDB respec-
tively.
3. Run the following BASIC program. This program assumes that the hardware address in
CFFO, if this is not the case, adjust line 10 for the proper address.
10DEF SEG = tiCFF0 hardware segment*
20CMDA = &h80: CMDB = &h81
30CMDC=ti9A:CMDD=&h9B
40POKE CMDA, 160 `set up from step 2 above
50POKECMDB, 17 `set up from step 2 above
60POKE CMDD, 255 `start conversion
70WHILE PEEK(CMDD) > 127 :WEND `wait until conversion is complete
80TOTAL = PEEKCCMDA) + PEEK `get high and low data and combine
CMDB)*256
90 VOLTS = TOTAL * 0.00015258
100 LOCATION 1,l:PRINT VOLTS, `print value in volts
110 GOT060
*Presumes interface is set to address CFFSO(h).
4. Adjust pot R8 so that the displayed voltage equals the DMh4 reading.
AMMlA-22
Theory of Operation
For the following discussion, please refer to the schematic diagram, drawing number 501-196.
AMMlA circuitry is divided into the following sections: local input multiplexer, programmable gain,
global input multiplexer, global gain amplifier, filter, A/D converter, A/D voltage reference amplifier,
and the IO-volt global reference.
Local Input Multiplexer
The local input multiplexer is made up of two 8 to 1 analog multiplexer Ul and U2, a dual analog switch
U3, and input protection resistor networks Rl and R2. The digital control signals for the input multi-
plexer are latched by U19, and additional digital logic to control the differential/single-ended mode se-
lection is in the PAL, U18. When the single-ended mode is programmed, U3 grounds the inverting input
of the differential instrumentation amplifier (pin 3 of U7), and connects the output of both Ul and U2
to the non-inverting input of the differential instrumentation amplifier (pin 3 of U5). The selected input
is switched through the appropriate 8 to 1 multiplexer to the differential amplifier input while the out-
put of the other 8 to 1 multiplexer is open circuited. When the differential input mode is selected, U3
connects the output of U2 to the inverting input of the differential instrumentation amplifier (pin 3 of
U7). The output of Ul is always connected to the non-inverting input of the differential instrumentation
amplifier (pin 3 of U5). The selected input channel -CH t erminal is connected through U2 and the +CH
terminals is connected through Ul to the local amplifier inputs.
Local Programmable Gain Amplifier
U4, U5, U6 and U7 make up the local programmable gain amplifier. U5 and U7 provide the high input
impedance, and also provide the voltage gain when the X10 gain is selected. When Xl gain is selected,
U4 (a dual analog switch) connects both U5 and U7 in the voltage follower configuration. When Xl0
gain is selected, U4 connects the inverting inputs of U5 and U7 to the taps on a voltage divider connect-
ed across the outputs of U5 and U7. The voltage difference between the inverting inputs of U5 and U7
is 1 /lO the voltage difference between the outputs of U5 and U7. This arrangement gives a voltage gain
of 10 for differential input signals and a voltage gain of 1 for common mode input signals. The common
mode input signal is defined as the average of the +CH and -CH input signals. The voltage gain in the
X10 mode is adjusted with R4, which adjusts the voltage divider ratio. The voltage gain in the Xl mode
is not adjustable. The outputs of U5 and U7 are connected to the precision resistor network Rll and am-
plifier U6. Rll and U6 make up a unity gain differential amplifier, which amplifies the differential signal
and rejects the common mode signal. The output of U6 is the overall amplifier output, and consists only
of the differential signal between U5 pin 3 and U7 pin 3.
Global Input Multiplexer
The global multiplexer selects which signal is measured by the A/D converter. U8 is a 16 to 1 analog
signal multiplexer. Inputs 0 and 14 of U8 are connected to ground. Input 1 is connected to the output of
the local amplifier. Inputs 2 through 10 go to pins on P14, and by external connections, are connected to
slots 2 through 10 of a Series 500 mainframe. These connections will carry the output signals of other
signal processing cards to the global multiplexer, where they can be routed to the A/D converter for
measurement. Inputs 11 and 12 also go to J14, but are typically not used. Input 13 is connected to the
IO-volt reference, and input 15 is connected to the +5-volt digital power supply The output of the mul-
tiplexer is connected to the Global Amplifier input.
Ah4MlA-23
Global Programmable Gain Amplifier and Filter
The global programmable gain amplifier is made up of U9, UlO, and Ull. The voltage gain of U9 is de-
termined by which tap on the precision resistor network R14 is selected by the analog multiplexer Ull.
The available gains are Xl, X2, X5, and X10. R14 is a voltage divider connected to the output of U9, and
the tap determined by Ull is connected to the inverting input of U9. The non-inverting input of U9 is
the overall input of the circuit. At the output of U9,lO volts represents a fuh scale input. The A/D con-
verter used cannot convert an input above 4 volts, so that output of U9 is reduced to 40% of its full scale
output by a divider made up of R15, R16, and R17. The analog filter is applied after this divider, and is
made up of C7 and R18 along with the combined resistance of the divider. For the 21612 pole, all resis-
tors are in the circuit, but when the 1OOkHz pole is programmed, FET Q3 is turned on and bypasses R18.
The 1OOkHz pole is determined by the equivalent output resistance of the 40% divider and C7. UlO buff-
ers the filter output and provides the low driver impedance required by the A/D converter. At the out-
put of UlO, 4 volts represents a full scale input. CRl, CR2, CR3, and CR4 make up a clipping circuit to
prevent overscale inputs from saturating the A/D, thus allowing immediate overload recovery.
A/D Converter
The A/D converter, U12, is a 12-bit successive approximation converter with an internal sample and
hold. This converter is similar to the A/D converter on the 16-bit AMM2 module in that both converters
read as 16bit converters. Like the AMM2, the AMMlA returns a high and low byte. However, the four
lowest order bits from the AMMlA are zeros, thus providing 12 effective bits of resolution. U12 oper-
ates on +5 volts and -5 volts. These supplies are derived from the +15 and -15 volt analog supplies by
U21 and U22 respectively. The A/D determines the ratio of the analog input to the voltage reference
input. The voltage reference used is 4 volts. The digital outputs of the A/D reference input. The voltage
reference used is 4 volts. The digital outputs of the A/D are buffered by U16 and U17. The logic control
for the A/D is in the PAL, U18.
A/D Voltage Reference Amplifier
The A/D converter requires a voltage reference source with a low output impedance from dc up to sev-
eral megahertz. U15, Ql, R8 and the associated components comprise an amplifier with the needed
characteristics. The reference voltage is derived from the heated zener reference U13 and divided down
to 4 volts by the divider made up of R8, R21, R22, and R24. Resistors R27 and R28 are used to restrict
the adjustment range of R8, and are either installed or not used based upon the zener voltage of Y13 at
the time of factory calibration. If U13 is replaced, it may be necessary to either install or remove either
one or both of these resistors. R31 and C6 frequency compensate the amplifier loop, and C9 is a titer
for zener noise.
10 Volt Global Reference
U13, U14 and the associated components form the 10 volt reference circuit. The zener voltage of approx-
imately 7 volts is ampli&cl by U14 to 10 volts. R7, R19, R20, and R23 determine the output voltage by
adjusting the gain of U14. R25 and R26 serve a function similar to R27 and R28 in the A/D reference
circuit. R30 and C8 filter the zener noise, and D7 assures that the circuit will start properly when power
is first applied.
AMhBA-24
AMMl A Troubleshooting Information
Diagnosing trouble with the AMMlA is best done in several steps. If the AMMlA is not functioning at
all, the following tests should be performed in the sequence indicated. It may be possible to skip some
of the tests if the AMMlA is partially functional.
A BASICA test program is listed at the end of this section which is used to setup the hardware for these
tests. Change line 10, if necessary, to the address segment used by your system. Each test is indepen-
dent, and can be run by itself if needed, as long as the first 3 lines of the program are also entered.
The overall test sequence is:
1. Check power supplies
2. Check reference voltages
3. Test digital control circuitry
4. Test local mux
5. Verify operation of local amplifier
6. Check operation of global amp
7. Test global mux
8. Verify operation of A/D converter
The only additional equipment needed for these tests is a digital multimeter (DMM), and two jumper
leads. When performing these tests, refer to schematic diagram 501-196, component layout 501-190, and
