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21-43.
The format of the error message is:
ERROR nn (CR)(LF)
The two digit number nn defines the error condition as listed in table 22-5. The carriage return (CR) and line
feed (LF) characters are the termination sequence used by analyzer whenever it transmitts information. All
characters are ASC II coded.
Table 2·1-5.
Error Messages
Error Code
Condition
00
Data requested without trigger
01
lnvolid mnemonic prefix
02
One character mnemonic (not T)
03
Invalid mnemonic suffix
04
Exponent overflow
05
Data underflow
06
Data overflow
07
Data transmitted, not allowed
08
Invalid data
09
RFinputpowerexceeded
10
Level or mod control error
21-44. To effectively utilize the error message capability oft he analyzer it is necessary to address the unit as a
talker after the transmission of each command string. The bus controller must then be programmed to
recognize the error message and to decode the error number. A successful data transmission will send back an
error code 00 when addressed as a talker. The controller should be programmed to ignore error 00 and to
display any other error to the operator. Of course if a valid output command followed bythetriggercommand
was sent, the talker address will result in the requested data being output to the controller.
21-45. Service Requests. There are only two conditions that will cause the analyzer to generate a service
request (SRQ) on the bus. If a SRQ is generated it must be cleared by a serial poll of the analyzer. The serial poll
is a bus command which results in a data byte being sent to the controller from the analyzer. The data byte
indicates the cause of the SRQ. Table 22-6 lists the SRQ causes and the corresponding serial poll data.
Table 21-6.
SRQ Data
Return Data
Condition
Binary
HEX
DEC
Depressing Cursor
01000001
41
65
Down Key
RF load over
01000010
42
66
Temperature
21-10
r
I
21-23. The following are examples of correct data fields for the value 12.34:
0.1234 E+2
+12.34
+0.1234 E2
12.34 E
1234 E-2
+1234 E-2
1234. E-2
12.34 EO
21-24. Command Strings. A command string consists of either a single command or multiple commands in
succession with or without embedded spaces. A command string must be terminated with a carriage return
and a line feed character.
21-25. Command Types. Each command is one olthree basic types, control selects (C). data entry (D), and
output requests (0). Type information for each command is listed in table 21-3.
21-26. Control Selects.
Control select commands select front panel switch settings. Some of these
commands do not require accompanying data, such as toggle switch commands.
21-27.
Data Entry.
Data entry commands replace manual entry of data through the keyboard. All of these
commands require data in the data field.
21-28. Output Requests.
Output request commands allow data that is normally displayed on the CRTto be
transferred to the controller. Accompanying data is not required with output requests. The data limits and units
listed in table 21-31or these commands refer to the return data. Output request commands cause the analyzer
to go to the proper display, function, and mode to acquire the designated reading. These states are listed in
table 21-3. The measurement however, is not made until a trigger command
'T'
has been sent from the
controller. The trigger command causes the measurement to be made and the data held lor transmission to the
controller. Then when the controller addresses the analyzer as a talker the data is output to the controller. A
reading can be retaken for any number of triggers without repeating the output request. The request is lost
however, when any command changing the display, function •. or mode is sent.
21-29. Trigger Command.
The trigger command is the exception to the two character command prefix.
This command is simply the letter
'T'
usually sent immediately following the output request command. II no
output request is pending, the trigger command is ignored.
21-30. Return Data. The data returned from the analyzer is formatted similar to the control data as shown:
±
n
E
-n
~
/
I
~
DATA SIGN
DATA VALUE EXPONENT SIGN EXPONENT MAGNITUDE
The data is always returned in this format with a single exception. Data lor the "RP", signal present, command
is returned as a single digit having a value of "0" or "1".
21-31.
Data Sign.
A+ or- character indicates the sign of the return data.
21-32.
Data Value. The data value is 1 to 5 digits in length with leading zero supression and no decimal
point.
21-33.
Exponent and Exponent Sign. The letter 'E' followed by a '-' character is always transmitted with
return data.
21-7
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