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1 1 1 C l l L l l l l l t L le
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H P 59401A Bus System Analyzer
(Figure 1) as a troubleshooting tool programming capabilities and then tener. By the nature of the actions
to help fulfill those needs. interfaces the instrument into the which they perform, some devices
system through a standard connec- may be only talkers (e.g., a paper
It is assumed that the reader is at tor. Figure 2 shows the bus struc- tape reader) or only listeners (e.g., a
least familiar with the IEEE-488 ture, connector, and IEEE-488 printer). Other devices such as a dig-
Interface Bus Standard and ter- Interface. ital voltmeter can be either a talker
minology. For those that are not, a or a listener. It is made a listener so
brief review is presented here but General Bus Description that it can be programmed for the
does not go into great detail. A more Physically, the bus itself is merely a correct voltage range and told when
detailed description of the bus is set of sixteen wires (along with a few
given in several of the references P 1
r assorted ground wires and an elec-
listed at the end of the article. trical shield) to which all devices on
that bus are connected (see Figure
What Is The Bus? 2). Eight of these wires serve to
r IEEE-488 is a concept carefully de-
fined for instrument communica-
tion. HP-IB is the implementation of
carry the data messages back and
forth over the bus. To maintain
order, only one device at a time can
the IEEE-488 Standard. In other place information on these d a t a
words, HP-IB, or GPIB, or IEEE-488 lines, and that device is known as
allows you to connect instruments the active talker. Any or all of the
together to form a "system" and other devices on the bus may sense
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I -
I
to take a reading. It is then made a Therefore: Listener - An "addressed" acceptor ?
talker so that it can put the results in the Data mode only.
of that reading on the data bus. true = low (0 V - 0.8 V)
false = high (2 V - 5.2 VI
Thus there is a need for one device Handshake Lines
on the bus to set up talkers and lis- Example: The handshake lines are used to con-
teners a t t h e proper time, issue NDAC true (low) = trol the timing of d a t a byte
instructions to the other devices on "none have accepted data" exchanges on the eight DIO signal
the bus, and in general to make sure NDAC false (high) = lines so that the source does not get
that all traffic on the bus proceeds in "all have accepted data" ahead of the acceptors. DAV is con-
a n orderly fashion. This device is NRFD true (low) = trolled by t h e source, whereas
called t h e active controller. Al- "none are ready for data" NDAC and NRFD are controlled by
though any device can be designed NRFD false (high) = I
the acceptors. The three handshake
with controller capability, a cal- "all are ready foi data" lines are:
culator or computer with its flexible
capability is usually assigned this BUS ma_.._ n-a-:i.
a ..-_
.._atruciure U~LUIIS NRFD -Not Ready For Data. When
task. As shown in Figure 2, sixteen signal set false (high) by an acceptor, it in-
lines comDrise the comDlete bus dicates to the source that the device
Finally, there is one and only one structure. Three are for data byte is ready to receive data.
special device on the bus known as transfer (handshake), five are for DAV - Data Valid. When set true
the system controller. This capabil- genera' interface and (low) by the source, it indicates that
ity is established by the hardware of eight are to data*The the data on the DIO lines is stable
the device itself (usually by the set- following definitions are used and available to be accepted by the
ting of a slide switch or a jumper) so throughout the remaining text. receiver.
that when power is turned on or the Source - A device transmitting in-
bus is reset, the device set to be the formation on the bus in either the NDAC - Not Data Accepted. When
system controller will also assume set false (high) by the acceptor, it in-
Command or Data mode.
the role of the active controller. At dicates to the source that data has
any time, the current active control- Talker - An "addressed" source in
been received. It does not mean the
ler may pass control to any other the Data mode only.
data was acted upon by the acceptor.
device on the bus that is capable of Acceptor - A device receiving in- What is does with the data is deter-
performing the functions of a con- formation on the bus in either the mined by the acceptor's internal
troller. (All devices are not required Command or Data mode. logic.
to have this capability.) The role of
system controller, however, stays
with the device which is physically TABLE 1. SUMMARY OF INTERFACE BUS DEVICES
set for that function and cannot be
passed off. At any time when the
system controller determines that I Device Description
I
something has gone wrong with the Listener A device capable of receiving data from other instruments. Exampleof
normal bus operations, it can reset this type of device are: display devices, programmablepower supplies,
the bus and regain active control. and programmable signal sources.
Refer to Table 1 for a summary of Talker A device capable of transmitting data (but not commands) to other
instruments. Examples of this type of device are: tape readers,
interface bus devices. voltmeters that are outputting data, and counters that are outputting
data.
Controller A device capable of managing communicationsover the bus such as
Negative-True Logic Description addressing and sending commands. A calculator or computer with an
appropriate I/O interface is an example of this type of device.
The interface bus uses the negative-
true logic convention to facilitate the System Controller This is an instrument on the bus which has all the features of a
wired OR (logical AND) use of the standard controller with the added ability to control the IFC and REN
NRFD and NDAC lines. Negative- lines. The system controller will take control of the bus when power is
true logic reduces noise susceptibil- turned on or the bus is reset or when it determinesthat something has
gone wrong with normal bus operations. The system controller can
ity in the true state and provides a pass control to other controllers but always retains the system
low power passive false condition controller status.
(high) on the lines when not in use.
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Instrument (Apparatus)
Capablilty ddlned by
Instrument Designer
Capabilitles deflned by IEEE-488
SH = Source Handshake
AH = Acceptor Handshake
T = Talker
TE = ExtendedTalker
L = Listener
, LE = Extended Llstenar
SR = Service Request
RL = Remote Local
PP = Parallel Poll
DC = Device Clear
DT = Device Trigger
C = Controller
Notes:
@= Interface bus slgnal lines
@= Remote interface messagesto and from Interface functlons
@= Device dependent messagesto and from device functions
@= State ilnkages between interface functlons
@= Local messagesbetweendevice functions and Interface functlons (messages to
interface functions am defined. messagesfrom interface functions exist accord-
r ing to tha deslgner's cholce)
@= Ramote interface messages sent by devlce functions wlthln a controller
WITH
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WITH
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q
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0 otner wre
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-
Interface Bus
01-End or
r Figure 2. interface Bus Structure. Note that the instrument can be conceptualized as
being partitioned into two areas: instrument functions and interface functions. But the
division does not necessarily imply two separate physical layouts
within the instrument.
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Typical Data Exchange SRQ - Service Request. This line is examples on a programmable digital /7
Using these lines, a typical data set true (low) any instrument r e
by voltmeter and used the analyzer to:
exchange would proceed as follows. questing service. The controller
All devices currently designated as identifies the device by a serial poll.
- Verify that the instrument com-
pletes the handshake cycle
active listeners would indicate (via No handshake is required when this
the NRFD line) when they are ready line is activated. - Address the instrument to its
for data. A device not ready would Remote mode
REN - Remote Enable. Only the
pull this line low (ground), while a
system controller can activate this - Program t h e instrument for
device that is ready would let the
line. When set true (low), the bus in- mode, function, range, trigger, etc.
line float high. Since a low overrides
struments become "enabled" (made
a passive high, this line will stay low - Cause the instrument to trigger
ready) to respond to a listen address
until all active listeners are ready or execute
from a controller which will place
for data. When the talker senses - Make the instrument a talker
them into the Remote mode. If REN
this, it places the next data byte on
ever goes false (high), all instru- and output its data onto the bus
the data lines and then pulls DAV
ments return to local operation.
low. This tells the listeners that the - Read the data and verify that it
information on the data lines is valid EO1 - End or Identify. This line is is correct
and that they may read it. Each lis- used to indicate the end of a transfer
tener (at its own speed) then takes sequence or, i n conjunction with
Obviously, if the instrument is less
the data and lets the NDAC line go ATN, to execute a parallel polling
complex such as a power supply or
high. Again, only when all listeners sequence. No handshake is required
switch, you can skip some of the
have let NDAC go high will the when this line is activated.
steps and use a less complex test
talker sense the situation of data ac- procedure. But whatever type in-
cepted. It can then remove DAV (let Data Input/Output (DIO) Lines
strument you are testing, by com-
it go high) and start t h e entire Eight lines carry information
sequence over again for the next
byte of data. A more detailed de-
bidirectionally between controllers,
talkers, and listeners. Normally the
pleting these tests you should be
able to isolate bus problems to the -7
handshake, DIO, or control lines,
scription of the handshake process is information is in the form of a 7-bit
and their associated logic within the
given in several of the references ASCII code with the eighth bit
instrument.
listed at the end of this article. available for parity (if desired).
Some devices, classed as "extended
General Interface Management listeners/talkers," require the full 8 You will also want to make sure
Lines bits in two bytes for addressing. In- your instrument responds to some of
Five interface signal lines are used formation transferred includes t h e commands listed in Table 2.
to manage an orderly flow of infor- interface commands, device addres- Check the instrument's Operating
mation across the interface. ses, and device dependent data. The Manual to see which ones apply.
IFC - Interface Clear. Only the sys- ATN command line is set true (low)
tem controller can activate this line. or false (high) by the controller t o
tell all the devices connected to the
When IFC is set true (low), all I/O
bus whether the DIO lines will carry Analyzer Operating Tips
operations cease and all talkers, lis-
a command or data. Preset the HP 59401A switches as
teners, and controllers go to the in-
follows:
active state. No handshake is
One-On-One Troubleshooting with
required when this line is activated.
the HP 59401A - LINE to on
ATN - All devices must monitor The HP 59401A Bus System Ana- - REN to true (up)
ATN at all times. When true (low), lyzer can be used to bench test and - MEMORY to OFF
ATN places the interface i n the troubleshoot any manufacturer's in- - COMP to OFF
Command mode where all devices strument t h a t is IEEE-488 bus - TALWLISTEN t o TALK
accept (handshake) data on the DIO compatible. - EXECUTE switch to HALT
lines and interpret it as commands. - SRQ, EO1 to 0 (down)
When false (high), ATN places the
interface in the Data mode where
Test Objectives
The following tests will show you
- ATN to 1 (UP)
3
device-dependent d a t a (e.g., pro- how to use the HP 59401A Bus Sys- The analyzer's display converts the
gramming or measurement data) is tem Analyzer to bench test all the DIO switch settings to their octal
carried between devices previously bus compatible functions of an in- value and that octal value to the
addressed to talk and listen. strument. We based some of the equivalent ASCII character.
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~ ~~ ~- __.
r For example: addition to the address switch, there
is usually a switch that is labeled
- Note the "new" octal number
is 061 (ASCII 1).
- Set the switches to
00 / 110 / 010 TALK ONLY/ADDRESSABLE.
- This is the instrument's listen
This switch must be set to AD-
- The display will show 2 / 062 DRESSABLE so the analyzer can address.
- Reverse bits 6 and 7 for enable the instrument to its Remote - Reverse bits 6 and 7. The DIO
01 / 010 / 010
.~ ~~~ ~~~
mode. switches should read 01 / 010 / 001.
- The display will show R / 122 The instrument's "basic address" is 5 - Note the "new'' octal number
bits long and is set by DIO bits 1-5. is 121 (ASCII Q ) .
Whatever value you set i n the Since the 59401A works in octal, the - This is the instrument's t a l k
switch register, the display will con- address must be loaded in octal. If address.
vert it to the ASCII/octal equivalent. your instrument address is listed as
More settings are shown in Table 3 a decimal number, convert it to octal After completing the above example,
and on the "Operating Instructions" with Table 3. note that the instrument's "basic
pull-out card in the front of the address" bits were not touched; how-
analyzer. Example: ever, the talk and listen bits 6 and 7
- An instrument's address is listed did alter the octal number. This will
When the lights (ATN, etc.) are lit, it be true of all instrument addresses.
as decimal 17.
means the line is true (low). When Bits 1-5 remain the same and you
the lights are out, it means the line - Table 3 shows decimal 17 to be change bits 6 and 7 to make i t a talk
is false (high). octal 021. or listen address. Refer to Figure 3.
- Set the DIO switches to
Therefore:
r N D A C ~ ~ ~ =
"none have accepted data"
00 / 010 / 001
- The display will show 021.
Set-Up Procedure
If your instrument requires a n
external stimulus, hook it up now.
NDAC not lit = Bits 6 and 7 are added to the "basic For example, if it's a DVM, connect a
"all have accepted data" address" to distinguish between a voltage (battery) to the terminals, or
NRFD lit = talk and listen address. For listen, if it's a power supply connect a load
"none are ready for data" bit 6 is "1"and b7 is "0". For talk, b6 to it. Connect the H P 59401A to the
NRFD not lit = is "0" and b7 is "1".The basic ad- instrument with the bus cable. Set
"all are ready for data" dress remains the same. the analyzer's switches as before
DAV lit = under the heading Operating Tips.
"data is valid" However, when you add bits 6 and 7
DAV not lit = to bits 1through 5, the whole octal
Testing the Handshake
"data is not valid" number changes as shown in the
and Listen Address
ATN lit = following example.
The following steps will:
"data byte is a command"
ATN not lit = Example: - check the DIO lines for open or
"data byte is data" shorted conditions
EO1 lit =
- As above, the basic address is
"end of data"
octal 021. - Check the handshake process
SRQ lit = - Now add in DIO switches 6 and 7 - address the instrument to i t s
"instrument requests service'' to form 00 / 110 / 001 Remote mode.
Device Addresses
Device addresses are used by the ac-
tive controller to specify who talks
and who listens on the bus. A
device's address is usually preset at
f the factory by an address switch or
jumpers. The switch usually con-
tains 5 bits and is typically located
on the outside rear panel of the in-
strument, but could be internal. In
1. Look up the instrument's ad- TROUBLESHOOTING TIP #1 - If the address was accepted, the /7
dress and write it down. If you can't REMOTE light on the instrument
find the address, go to step 5. Each time you press EXECUTE, the will light. If there is no indicator for
handshake lights should perform as the Remote mode, then switch ATN
2. Set the DIO switches to the in- follows: down (false) and watch the NDAC
strument's "basic address." Note light. If it goes out, the address was
EXECUTEin -
that if the address is provided as a not accepted. If it stays lit, you have
DAV on, NRFD on, NDAC o f
f.
decimal number, you can convert it found the address and the instru-
to octal with Table 3. EXECUTE out - ment is in its Remote mode. The rea-
DAV o f NRFD off,NDAC on.
f, son it stays lit is that the instru-
3. Set bit 6 up and bit 7 down. This ment's internal logic has responded
converts the instrument's "basic ad- Remember that DAV is controlled by to the address and allowed the inter-
dress" to its listen address. the HP 59401A' and NRFDNDAC are face to proceed to the next step in the
held low by the instrument. handshake cycle. Remember that a
4. Press and hold EXECUTE. DAV device t h a t is unaddressed must
and NRFD will light and NDAC will Hint-NRFD and NDAC cannot handshake every address but get off
go out. Release EXECUTE. This in- both be false (indicators off) at the the bus during a data transfer. (Note
dicates t h a t t h e handshake was same time. that when you switch ATN down
completed (refer to Tip #l).It does (light off) you are telling the bus
not mean that the address was acted that the next data byte will be data
upon by the instrument. What i t Searching for the Listen Address and not a command.)
does with the data is determined by and Testing the DIO Lines
the instrument's internal logic. 5. Complete the following steps if 8. Repeat this process for the next
you cannot find the instrument's ad- address of 041 (ASCII !), then 042,
- If the address was accepted, the dress, or if you believe the DIO lines 043, etc. Continue this process until
REMOTE light on the instrument
will light. If there is no indicator for
are bad. If you have successfully set
the instrument to its Remote mode,
you have tested all 31 combinations
of bits 1-5. During this procedure
3
the Remote mode, then switch ATN go to step 9. you should discover the correct lis-
down (false) and watch the NDAC ten address for t h e instrument.
light. If it goes out, the address was 6. Set the DIO switches as follows: WRITE IT DOWN!.
not accepted (refer to Tip #2). If it
stays lit, the instrument has ac- - b8=O TROUBLESHOOTING TIP #2
cepted the listen address in Remote - b7= 0
and is now ready for the next data - b6= 1 If the instrument does not go into its
byte. The reason it stays lit is that
the instrument's internal logic has
- b5
. =o
0
Remote mode, the DIO lines may be
open or shorted, or the instrument's
internal logic may be bad. To check
responded to t h e address and for "shorts," perform steps 5 through
allowed the interface to proceed to - bl
8 and make certain the octal readout
the next step in the handshake cycle. changes each time you change an
Remember that a device that is un- 7. The octal readout on the H P address switch. To check for
addressed must handshake every 59401A will be 040 and the ASCII l t opens,'' go to the address lines
address but get off the bus during a character will be a blank or SP inside the instrument and monitor
data transfer. (Note that when you (space). Press and hold EXECUTE. them with a logic probe as you are
switch ATN down (light off) you are DAV and NRFD will light and switching. Also check the internal
telling the bus the next data byte NDAC will go out. Release EXE- addressing logic to make sure it's
will be data and not a command.) CUTE. This indicates that the hand- functioning properly.
shake was completed (refer to Tip
#l).It does not mean that the ad- 9. At this point the instrument
dress was acted upon by the instru- should be in its Remote mode sitting
ment. What it does with the data is there waiting for you to tell it what
determined by t h e instrument's to do next. If not, refer to Tip #2.
internal logic. Otherwise continue reading. 3
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r Programming the Instrument
Programming your instrument in-
10. Set the HP 59401A switches as
follows:
data available on the bus so you can
read it with the analyzer.
volves using the HP 59401A as a
controller to send some precise pro- - REN to true (up) Set the instrument's talk address
gram codes that will set the instru- - MEMORY to OFF into the DIO switches. Remember
ment's range, function, mode, etc. - COMP to OFF that the talk address has b7 up and
These codas mnst he nht,ninpd frnm - TAT.K/T.TSTFIN t.n T A 1 . K
I_---I--
- EXECUTE switch to HALT
- SRQ, EO1 to 0 (down) 19. Press EXECUTE. The instru-
- ATN to 1 (UP) ment should now be a talker and
FUNCTION output its data onto the bus. Set the
DC Volts = F1 TALK/LISTEN switch to LISTEN.
AC Volts = F2 11. Set the DIO switches to the in-
strument's listen address and press This makes the analyzer a listener
OHMS= F3 and since the instrument is a talker,
EXECUTE. This reaffirms that the
RANGE instrument is in its Remote mode. the DAV indicator should light. The
. l =R1 (Note that this is a command word SRQ indicator may or may not be
1 = R2 because ATN is set to 1 (true)). lit-it depends on each individual
10 = R3 instrument. The first data byte from
100 = R4 the instrument should be displayed.
12. Change ATN to 0 (false). This Write the reading down on a piece of
Note that these codes are considered means that the next word sent to the paper. Each timc3 you press EXE-
data words and must be sent with instrument will be a data word. CUTE, the next data byte is read
>:--l--.
~ I ~ L ILIW ulsplay. Be sure and write
:-A-
ATN false. LL-
J
13. Set the DIO switches to the first each one down.
Some instruments also recognize program code word.
64 general IEEE-488 commands that
will cause the instrument to get off Example:
- If the analyzer's display is all
zeros, check that the instrument was
the bus (become "unaddressed") or triggered, and check t h a t the in-
set itself to a pre-determined state or - Function = ASCII F = octal 106 strument is a talker.
initiate a n action. These commands - The DIO switches would be
are listed in Tables 2 and 4. Note Hint - Each time the instrument is
01 / 000 / 110 triggered, it should give you indica-
that since these are commands ATN
must be true. tion (e.g., front panel indicators
14. Press EXECUTE. change or a gate light flashes).
All of the following steps are totally
15. Set the DIO switches to the next - If the data is meaningless, re-
dependent on how the functions of
program code word. check the program codes and retrig-
your instrument are programmed
(i.e., function, mode, range, trigger, ger the instrument.
Example:
etc.). Refer to your Operating Man-
ual and look for a description or Hint - Some i n s t r u m e n t s use a
- DC Volts = ASCII 1 = octal 061 storage buffer between the displayed
table of GPIB (or HP-IB) program
data and the bus.
codes. Read it carefully and write - The DIO switches would be
down the ASCII characters of the 00 / 110 / 001
functions you want to program. You 20. Refer to t h e instrument's
Operating Manual to determine the
can use Table 3 to convert these 16. Continue sending the codes un- format of t h e transmitted data.
ASCII codes to octal numbers. til your instrument is fully When you get to the end of the data
programmed. reading, the analyzer's EO1 light
NOTE
may light (true) indicating the end
When you set the DIO switches 17. If you decide to try the Group of the data byte. In Hewlett-Packard
on the analyzer, pay close at- Execute Trigger (GET) command to instruments, the last data byte is
f tention as to whether you are
sending a command or data
trigger your instrument, don't forget
to set ATN true.
usually LF (line feed) which is octal
012 (i.e., when you see 012 EO1
word. Remember; should light). You must check the
ATN = 1 (true) = command 18. Once the instrument is pro- instrument's Operating Manual to
word grammed and triggered, you want to see if EO1 is pulled true at the end of
ATN = 0 (false) = data word address it as a talker to make the the data string.
Summary TABLE 2. SUMMARY OF BUS COMMANDS
This completes the test. In sum- THAT MOST INSTRUMENTS WILL RECOGNIZE
mary, you have performed the fol-
lowing steps: GPlB OCTAL
COMMAND CODE CODE PURPOSE
- Verify that the instrument com-
pletes the handshake cycle. UNLISTEN UNL 077 Clears Bus of all listeners.
- Addressed the instrument and UNADDRESS
COMMANDS
caused it to respond. UNTALK UNT 137 Unaddresses the current talker so
that no talker remains on the Bus.'
- Told the instrument to complete
its assigned task; i.e., take a meas- Local Lockout LLO 021 Disables front panel local-reset
urement, output a voltage, etc. button on responding devices.
- Made the instrument a talker Device Clear DCL 024 Returns all devices capable of
and output its data onto the bus. responding to pre-determined
states, regardless of whether
- Read the data and verified that it they are addressed or not.
was correct.
Parallel poll PPU 025 Sets all devices on the HP-IB
Admittedly this is a simplified pro- 'OMMANDS Unconfigure with Parallel Poll capability to
a predefined condition.
cedure for a complex standard. I t
cannot exercise an instrument in the Serial Poll SPE 030 Enables Serial Poll Mode on
sophisticated manner of a calculator Enable the Bus.
or computer controller. But then you
would have to write programs for the Serial Poll SPD 031 Disables Serial Poll Mode on
Disable the Bus.
calculator/computer and it would not
allow you to wiggle each line of the Selective SDC 004 Returns addressed devices,
bus separately and watch the re- Device Clear capable of responding to
sults. It is this close monitoring of pre-determined states.
bus activity with the HP 59401A
Go to Local GTL 001 Returns responding devices to
that allows you to isolate problems local control.
faster.
Group Execute GET 010 Initiates a simultaneous
If you have any comments on this Trigger pre-programmed action by
article or suggestions for an upcom- responding devices.
ADDRESSED
ing system troubleshooting article, COMMANDS
This command permits the
Parallel Poll PPC 005
please contact the editor at the ad- Configure DIO lines to be assigned to
dress listed on the back page of instruments on the Bus for the
Bench Briefs. purpose of responding to a
parallel poll.
References: TCT 011 This command is given when
Take Control
IEEE Std 488-1978; Condensed De- the active controller on the
scription of the Hewlett-Packard Bus transfers control to
Interface Bus (HP p/n 59401-90030); another instrument.
Tutorial Description of t h e
UOTE: Talkers can also be unaddressed by transmitting an unused talk address on the Bus.
Hewlett-Packard Interface Bus (HP This is not true with listeners.
p/n 59300-90007); Interfacing Con-
cepts and the 9825A (HP p/n 09825-
90060); HP-IB Troubleshooting, an
H P service training course created
by Les Young, HP Mt. View.
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TABLE 3. ASCII TO BINARY TO OCTAL TO DECIMAL
CONVERSION TABLE
ASCII Character Codes
ASCII EOUIVALENT FORMS ASCII EOUIVALENT FORMS ASCI EOUIVALENT FORMS ASCII EOUIVALENT FORMS
Elnary Octal DOC Blnary Oclal Dee Elnary 0Ct.l Dee
-
Char. Char. Char
- -
Char. Elnary 0Cc.l Doc
NULL 00000000000 0 space 00lOOOOO 040 32 @ OlOOOOOO 100 64 011m 140 96
SOH OOOOOOOl 001 1 ! WlooOol 041 33 A 0 1 m 1 0
11 65 a 011ooOol 141 97
STX WOOOOlO 002 2 001m10 042 34 E 01m10 102 66 b 01lOOOlO 142 98
ETX WOOOO11 003 3 # WlooOll 043 35 C Olooooll 103 67 C 011m11 143 99
EOT woo0100 004 4 $ 00100100 044 36 D 01m100 104 68 d 01100100 144 100
EN0 woo0101 005 5 % 00100101 045 37 E 01m101 105 69 e 01100101 145 0
11
ACK 00000110 006 6 8 00100110 046 38 F 01m110 106 70 f 01100110 146 102
BELL woo0111 007 7 WlWIll 047 39 G 0 1 ~ 1 1 1 107 71 9 01100111 147 103
BS oom
oo1 010 8 ( w101m 050 40 H 01001m I10 72 h 01101m 150 104
HT ooool001 011 9 1 00101001 051 41 I 01001001 111 73 I 01101001 151 105
LF oooo1010 012 10 00101010 052 42 J 01001010 112 74 i 01101010 152 lo6
VTk? WOalOll 013 11 + 00101011 053 43 K 01001011 113 75 k 01101011 153 107
FF oooO1100 014 12 00101100 054 44 L 01001100 114 76 I 01101100 154 108
CR oooo1101 015 13 - 00101101 055 45 M 01001101 115 TI m 01101101 155 109
so ~ 1 1 1 0 016 14 00101110 056 46 N 01001110 116 78 n 01101110 156 110
SI ~ 1 1 1 1 017 15 / 00101111 057 47 0 01001111 117 79 0 01101111 157 111
DLE ooOloo00 020 16 0 Wloo
loo 060 48 P 0101oooo 120 Bo P 0111m 1M 112
DCI 11
mm 021 17 1 0011m1 01
6 49 0 0101m1 121 81 q 0 1 1 1 ~ 1 11
6 113
DCz m10010 022 18 2 00110010 062 50 R 01010010 122 82 r 01110010 162 114
DC, ~ 1 0 0 1 1 023 19 3 00110011 063 51 S 01010011 123 83 S 01110011 163 115
DC4 ~ 1 0 1 0 0 024 M 4 00110100 064 52 T 01010100 124 84 t 01110100 164 116
NAK m10101 025 21 5 00110101 065 53 U 01010101 125 85 U 01110101 165 117
SYNC ~ 1 0 1 1 0 026 22 6 00110110 066 54 V 01010110 126 86 V 01110110 166 118
ET6 ooO10111 027 23 7 00110111 067 55 W 01010111 127 87 W 01110111 167 119
CAN ooOllooO 030 24 E 0011looO 070 56 X 01011m 130 88 X 0 1 1 1 1 ~ 170 1x)
EM m11001 031 25 9 00111001 071 57 Y 01011001 131 89 Y 01111001 171 121
SUB OOol1010 032 26 00111010 072 58 2 01011010 132 90 2 01111010 172 122
OOoIlOll 033 27 00111011 073 59 [ 01011011 133 91 { 01111011 173 123
ESC
< 00111100 074 60 \ 01011100 134 92 01111100 174 124
FS 00011100 034 28
- 00111101 075 61 I 01011101 135 93 I 01111101 175 125
GS OOolllOl 035 29 ~
RS 30011110 036 30 , 00111110 076 62 01011110 136 94 01111110 176 126
us 00011111 037 31 7 00111111 077 63 - 01011111 137 95 DEL 01111111 177 127
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TABLE 4. ALL TALK AND LISTEN ADDRESS COMBINATIONS WITH
ADDRESSED AND UNIVERSAL COMMANDS
ASCIIASO & IEEE CODE CHART
I
BITS
NUMBERS
CONTROL SYMBOLS UPPER CASE LOWER CASE
0 4 83 82 B1
0 20 40 60 100 120
0 0 o 0 NUL o OI DLE16 20
SP 32 30
0 48 40
@ 64 50
P e
1 GTL 21 LLO 41 61 101 121
0 B 0 I SOH 1 11DC117 ! 1 A Q
21 3 1 31 49 41 65 51 e 61 97 71 113
8 0 1 0
2
---_ ---
STX DCZ
22 42
II
"
62
2
- 102
-
B
122
~
R
142
b
162
r
2 2 12 18 22 34 32 50 42 66 52 82 62 98 72 114
23 63 103 123 143 163
a D
. . I I
. . 3ETX
3
-. ..
3/13
- DC3
-- 43
19123
#
" 35133
3
- 51143
-
C
67153
-
S
83163
-
e
99173
-
c
115
1
14 SDC124 DCL144 I64 1104 1124 1144 I164
0 1 o 0 EOT 4 14DC420 24
$
36 34
4 D T
52 44 68 54 84 I16
5 PPC 25 PPU 45 65 105 125 5
; 100i;;5
B 1 0 1 ENQ 5 15NAK21 25
'o
/
37 35
5 53 45
E 69 55
U 85 65 101 75 117
6 26 46 66 106 126 146 166
0 i 1 0 ACK
6 16
SYN
22 26
8 38 36
6
54 46
F
70 56
V
86 66
f
102 76
V
118
0 1 1 1
7
BEL
27
ETB
47
' 67
7
107
G
127
W
147 167
W
7 17 23 27 39 37 55 47 71 57 17 67 i n 3 77 119
10 GET 30 SPE 50 70 110 130 150 170
* 8 Bs 8 1SAN24 28 ( 40 38
8
56 48
H 72 58
X
88 68
h
104 78
X
120
11 TCT 31 SPD 51 71 111 131 151 171
i O O i g H T9 19 EM 25 9 I
73 59