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Addendum to the AOMI Manual
The following information covers changes to the manual for the AOM1/2 and AOM1/5
modules:
ERROR IN DESCRIPTION OF STROBE OPERATION
The topics "D/A DATA" and "STROBE" on pages 6 and 7 of the AOMl manual imply that
the mechanism of updating an output channel depends on the strobe feature, which may be
enabled or disabled. This information is in error. The strobe operation is always enabled. A
channel will update & after the strobe line has been sent an "ISSUE DATA" command,
Several channels may be loaded with data and an ISSUE DATA sent to the strobe line, or
channel data may be updated individually, each followed by an ISSUE DATA,
This information is relevant only if you are writing your own low-level drivers for the AOMl
module. High-level software such as KDACSOO,ASYST, or Labtech Notebook handle
updating of output channels automatically.
Document SOO-929-02BAddendum to the AOMl Manual
(c) Keithley Instruments, Inc. Cleveland, OH April 2.5, 1991
AOMl
Analog Output Module 1
The AOMl Analog Output Module is available in two versions. The AOM1/2 provides
two channels, while the AOM1/5 provides 5 channels of high-speed analog output.
Each channel has an independent D/A converter.
The D/A converters offer true l2-bit resolution with a maximum nonlinearity of
~0.012%. Five switch-selected output ranges are available for each converter: 0 to +lOV,
0 to +5V, unipolar; *lOV, f5V, *2.5V, bipolar.
A system strobe feature, supported by two levels of data latching in the D/A converter,
allows any number of D/A channels to be updated simultaneously.
Signals are connected directly to the module via screw terminals mounted on the right-
hand side of the module board.
The AOMl module may be placed in any available slot in the system. To install the
module, first turn off the power and remove the top cover of the mainframe. Insert the
module in the desired slot with the component side facing the power supply. General-
ly, analog modules should be placed in the low-numbered slots to isolate them from
power supply thermal and noise effects.
CAUTION: Always turn off the system power before installing or removing modules.
To avoid possible EM1 radiation, never operate the system with the top cover removed.
User-Configured Components
Each D/A converter installed on the AOMl offers five output ranges: 0 to +5V, 0 to
+lOV, -5 to +5V, -10 to +lOV, and -2.5 to +2.5V. Switch Sets SlOES105 on the
AOM1/5 independently select the output ranges for channels O-4, respectively. On the
AOM1/2, SlOl and S102 select output ranges for channels 0 and 1.
All output connections are made to screw terminals. Two terminals are provided for
each channel: signal output and a common ground. All terminals accept 16-24 gauge
wire stripped to 3116 of an inch. See Table 1 and Figure 1 for a list of AOMl user-
configured components.
Document Number: 500-929-01 Rev. B AOMl-1
Table 1. Summary of User-Configured Components on the AOMl
Name Designation Function
Switch 101 SlOl Analog Output Range Channel 0
Switch 102 s102 Analog Output Range Channel 1
Switch 103 s103* Analog Output Range Channel 2
Switch 104 s104* Analog Output Range Channel 3
Switch 105 s105* Analog Output Range Channel 4
Screw Terminals J145 Output Connection Channels O-4
*AOM1/5only
Figure 1. AOM1/5 Module (AOMV2 is similar except, it has components only
for channel 0 and 1.)
Connections
Connecting terminals on the AOMl are shown in Figure 2, which illustrates a typical
connecting scheme. The use of shielded cable is recommended to minimize the
possibility of EM1 radiation. Connect the shield to AOMl ground. Leave the other end
of the shield disconnected.
AOMl-2
LOAD
Figure 2. Typical AOMl Output Connections (Channel 0 shown)
Range Switches
The AOM1/2 has two switch sets, SlOl and S102 that control the output range of chan-
nels 0 and 1. The AOM1/5 has five switch sets, SlOlS105 that control the output range
of channels O-4 respectively. Each switch set has five individual DlP switches that con-
trol the range for that channel. The settings for these five individual switches are
shown in Table 2. Each channel is identical in operation. Note that changing ranges will
require calibrations described in the servicing section of this manual.
Table 2. DIP Switch Settings for Switch sets SlOl and S105
Output Range DIP Switches
1 2 3 4 5
0 to +5v Closed Open Closed Closed Open
0 to +loV Closed Open Open Closed Closed
*2.5V Open Closed Closed Closed Open
*5v Open Closed Open Closed Closed
*1OV* Open Closed Open Open Closed
*Factory default settings
Note: DIP Switch settings are the same for all switch sets.
AOMl-3
Output Limitations
There are certain restrictions as to the output capabilities of each channel on the AOMl
module. Generally, there is an upper limit on the amount of capacitance and a lower
limit to the resistance that can be connected across the output. To avoid possible oscilla-
tion, output capacitance must be less than lOOOpF. Similar restrictions apply to the out-
put current, which is determined largely by the resistive component of the load con-
nected across the output. If the resistance is too small, accuracy will suffer. To maintain
rated accuracy, the load resistance should be no smaller than 5kQ with a maximum of
output of *NV. Output current limit is 2-3mA.
Figure 3 shows a simplified diagram of an AOMl output stage. Because the output is
directly sensed, a certain amount of voltage drop across the internal resistance is
tolerated.
0
FROM A/D
CONVERTER
SIGNAL
GROUND
Figure 3. AOMl Output Stage
Commands
AOMl module commands are listed in Table 3. Table 4 summarizes the locations for
slot-dependent commands.
Table 3. Command Used with the AOMl Module
Command Location
D/A CONTROL Slot-dependent CMDA
D/A DATA Slot-dependent CMDB
STROBE: CFF9D
AOMl-4
Table 4. Locations for Slot-Dependent Commands
Slot CMDA CMDB
Slot 1 CFFSO CFF81
Slot 2 CFF82 CFF83
Slot 3 CFF84 CFF85
Slot 4 CFF86 CFF87
Slot 5 CFF88 CFF89
Slot 6 CFF8A CFFSB
Slot 7 CFF8C CFFSD
Slot 8 CFFSE CFFSF
Slot 9 CFF90 cFF91
Slot 10 CFF92 CFF93
D/A CONTROL
Location: Slot-dependent CMDA
D/A CONTROL always precedes D/A DATA, indicating to the AOMl module which
channel of analog output to update, and which byte of data to load. Table 5 lists values
written to the D/A CONTROL locations.
The high and low bytes of data may be updated independently and in any order; there
is no hardware reason that both bytes must be updated at the same time. Similarly,
channels can be updated independently and in any order.
The location assigned to D/A CONTROL varies depending on which baseboard slot
holds the D/A converter being addressed (see Table 4).
Table 5. Values Written to D/A CONTROL
Function .Binary HeX Decimal
Channel 0 Low Byte 0000 HO 0
Channel 0 High Byte 0001 Hl 1
Channel 1 Low Byte 0010 H2 2
Channel 1 High Byte 0011 H3 3
Channel 2 Low Byte 0100 H4 4
Channel 2 High Byte 0101 H5 5
Channel 3 Low Byte 0110 H6 6
Channel 3 High Byte 0111 H7 7
Channel 4 Low Byte 1000
Channel 4 High Byte 1001 iii 9
8
Note: AOM1/2 has only channels 0 and 1.
DIA DATA
Location: Slot-dependent CMDB
D/A DATA is used to load data values into the D/A converter. This command should
AOMl-5
always be preceded by D/A CONTROL, which selects the channel and the byte to be
loaded. The data must be separated into low and high bytes prior to loading, and each
byte must be prefaced by D/A CONTROL.
When the strobe feature is not enabled, the output of the converter is updated im-
mediately. Thus, when the strobe is not used, the low and high bytes are updated in-
dependently. When the strobe is enabled, outputs are not updated until the STROBE
command is issued with the value 1 (to issued data).
The digital value loaded into the converter varies according to the output range selected
via the range switch set, To determine the digital value to input for a given voltage, it is
necessary to know the output range of the D/A converter. With a K&bit digital con-
verter, there are 4096 possible voltage levels, specified with digital values o-4095.
Therefore the actual full scale value is the nominal f.s. value minus 1 LSB. The voltage
of each step equals the range divided by 4095. For an input range of 0 to +lOV, for ex-
ample, the voltage of each step is lo/4095 or 0.002441: hence, a formula for each voltage
range can be derived (See Tables 6 and 7).
Where V is volts and D is the digital value loaded into the converter. Similarly, the
following equations determine the digital value to use when a particular voltage is
required.
Table 6. Digital Values to Volts
Output Range Voltage
0 to +lOV V = D * 0.002441
0 to +5v V = D * 0.001221
-10 to +lov v- -10 + (D * 0.004882)
-5 to +5v v =-5 + (-II * 0.002441)
-2.5 to +2.5V V = -2.5 + (D * 0.001221)
Table 7. Volts to Digital Values
Output Range Digital Value
0 to +lov D = INT(V10.002441)
0 to +5v D = INT(V/O.OOl221)
-10 to +lOV D = INT(V10.004882) + 2048
-5 to +5v D = INT(V/O.O02441) 2048
+
-2.5 to +2.5V D = INT(V/O.OOl221) 2048
+
STROBE
Location: CFF9D
The STROBE command is used to make possible the synchronous updating of two or
more analog output channels. STROBE is issued in three modes: strobe enable, strobe
disable, and issue data. The STROBE feature must either be enabled or disabled at the
start of any Program, or the converters will not function (see Table 8).
AOMl-6
When any strobe feature is disabled, all data given to a D/A converter is immediately
placed in that converters primary data latch, and the voltage output updated. The low
byte and high byte are thus updated asynchronously.
When the strobe is enabled, no data is updated until the STROBE command has been
issued in the issue data mode. Instead, new data is placed in a secondary data latch
within the D/A converter. When the STROBE command (to issue data) is given, the
new data is released to the primary data latch, updating the voltage output, and old
data in other channels is reissued, leaving the voltage output of these channels un-
changed. The strobe is completely flexible. Any amount of data--from a single byte to
any number of channels--can be updated when the strobe is enabled.
To use the strobe, issue the strobe enable command early in the program. Use the D/A
CONTROL and D/A DATA commands to load the secondary latches of the appropriate
converters, This can be done as far in advance as required. To issue the new data, load
STROBE with 1 (to issue data), releasing all data loaded since the last issue data com-
mand and leaving unchanged the outputs of other channels.
The STROBE feature is global, affecting all D/A modules installed in the HTMS 1000.
Table 8. Values Written to STROBE
Function Binary HeX Decimal
Strobe Enable 01ooooO0 H40 64
Strobe Disable 10000000 H80 128
Issue Data 00000001 HO1 1
AOMl Module Calibration
The AOM modules should be calibrated whenever the range is changed. Because a con-
siderable amount of programming is necessary, a program is presented in this manual
as an aid in calibrating these modules. Program 1 is designed for the AOMl. Use the
following procedure when calibrating this module.
1. Place the AOM module to be calibrated in slot 5. Set the output range as indicated in
Table 9.
2. Enter the program into the computer.
3. Connect the DMM high input lead to the signal terminal of the channel being
calibrated. Connect the DMM low lead to module ground. For maximum accuracy,
connect the usual load resistance between the signal terminal and ground.
4. Run the program and follow its instructions. Refer to Figure 4 for adjustment loca-
tions. Make sure the output range of the module is set correctly. The program will
prompt with the correct range switch settings.
5. Repeat the procedure as necessary with the remaining channels.
AOMl-7
CHAN 0 OFFSET
CHAN 0 GAIN
CHAN 1 OFFSET
CHAN 1 GAIN
1
;!?
:Y
CHAN 2 OFFSET
CHAN 2 GAIN
CHAN 3 OFFSET
CHAN 3 GAIN
CHAN 4 OFFSET
CHAN 4 GAIN
Figure 4. AOMl Module Calibration Adjustments
AOMl-8
Table 9. AOMl Output Range
Output Range DIP Switches
1 2 3 4 5
0 to +5v Closed Open Closed Closed Open
0 to +lov Closed Open Open Closed Closed
k2.5V Open Closed Closed Closed Open
*5V Open Closed Open Closed Closed
*loV Open Closed Open Open Closed
Program 1. AOMl Calibration
10 DEF SEG = &HCFFO:CLS
20 CA=&H88:CB=&H89:ST=&H9D
30 POKE ST, 64
40 PRINT "INSERT AOMl INTO SLCYT5"
50 PRINT: INPUT `XOMl CHANNEL (O-4)"; CH
60 IF CHcO OR CH>4 THEN 50
70 PRINT: PRINT "CONNECT DMM To CHANNEL"; CH
80 PRINT: PRINT "RANGE SWlTCH POSITIONS"
9OPRINT"12345"
1ooPRlNlYom +5vcocco"
110PRINT'20To +1ovcoocc"
120 PRINT"3 +2.5V 0 C C C 0"
130 PRINT"4 +5v 0 c 0 c c"
14OPRINT"5 +1ovocooc"
150 PRINT: INPUT "RANGE (l-5)"; R
160l'RINT:IfR < 1OR > 5THENl.50
170 ON R GOSUB 300, 310, 320, 330, 340
180 POKE CA, TCH: POKE CB, 0
190 POKE CA, TCH + 1; POKE CB, 0
200 POKE ST, 1
210 PRINT: PRINT `ADJUST CHANNEL"; CH;"OFFSET FOR"; L$;"VOLT READlNG ON
DMM"
220 INPUT "PRESS RETURN TO CONTINUE"; A!