HP 8921A Programmer's Manual page 553

Table 52 Comments For SRQ Example Program (Continued)
Program Line
Number
2040 * Call Processing Status Register Group Condition register conditions which will set the
Summary Message TRUE if they occur:
Therefore set the Call Processing Enable Register to 63: STAT:CALLP:ENAB 63
* The Call Processing Status Register Group Summary Message is passed to the Status
Byte Register through Bit 9 in the Operational Status Register Group Condition Register.
The Operational Status Register Group must be configured to set its Summary Message
TRUE if the Summary Message from the Call Processing Status Register Group is
TRUE. Therefore Bit 9 (2^9=512) in the Operational Status Register Group Enable
Register must be set HIGH: STAT:OPER:ENAB 512
* The Test Set's HP-IB interface has a large input buffer and can handshake in several
commands. The commands are processed serially out of the input buffer. In this example
program the Cnfg_srvc_intrp sends 8 commands to the Test Set in rapid succession.
The *RST command requires several seconds to execute. Since the Test Set can
handshake in many commands it can appear to the control program that the Test Set has
executed all of the commands sent, when in reality they have only been placed in the
input buffer. To prevent the control program from getting ahead of the Test Set the
*OPC? query command is used to synchronize the Test Set and the control program.
3000 The Srvice_interupt subprogram first checks for errors. If an error is detected from one of
the enabled registers the Error_flag is set and the subprogram is exited. If an error is
detected from a non-enabled register the program stops. If no errors are detected then the
Call Processing registers are queried to clear them to allow further interrupts and the
operation complete bit is set. In a 'real world' situation the Srvice_interupt subprogram
should take some action if the Call Processing subsystem did not generate the interrupt (if
the command IF BIT(Status_byte,7) was not true). This branch is left out of the example
subprogram to minimize the number of program lines. As written, the subprogram assumes
that the interrupt was caused by the desired call processing activity completing
successfully.
6080 Ptr_value is the value that the positive transition filter will be set to. The value is
determined by which pseudo-LED will light when the desired command is completed. For
example, a successful PAGE is indicated by the Connect pseudo-LED lighting. Therefore
the Ptr_value is set to 32 (2^5) for the Page command.
Bit 5: Connect LED lit
Bit 4: Access LED lit
Bit 3: Page LED lit
Bit 2: Unused in Test Set
Bit 1: Register LED lit
Bit 0: Active LED lit
32+16+8+4+2+1 = 63
Chapter 8, Programming The Call Processing Subsystem
Comment
decimal value = 2^5 = 32
decimal value = 2^4 = 16
decimal value = 2^3 = 8
decimal value = 2^2 = 4
decimal value = 2^1 = 2
decimal value = 2^0 = 1
Example Programs
553