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Serial Poll
The HP 16500C Logic Analysis System supports the IEEE 488.1 serial poll
feature. When a serial poll of the instrument is requested, the RQS bit is
returned on bit 6 of the status byte.
Using Serial Poll (HP-IB)
This example will show how to use the service request by conducting a serial
poll of all instruments on the HP-IB bus. In this example, assume that there
are two instruments on the bus: the Logic Analysis System at address 7 and a
printer at address 1.
The program command for serial poll using HP BASIC 6.2 is
Stat = SPOLL(707). The address 707 is the address of the Logic Analysis
System in the this example. The command for checking the printer is
Stat = SPOLL(701) because the address of that instrument is 01 on bus
address 7. This command reads the contents of the HP-IB Status Register
into the variable called Stat. At that time bit 6 of the variable Stat can be
tested to see if it is set (bit 6 = 1).
The serial poll operation can be conducted in the following manner:
1 Enable interrupts on the bus.
This allows the controller to see the SRQ line.
2 Disable interrupts on the bus.
3 If the SRQ line is high (some instrument is requesting service) then
check the instrument at address 1 to see if bit 6 of its status register is
high.
4 To check whether bit 6 of an instruments status register is high, use
the BASIC statement IF BIT (Stat, 6) THEN
5 If bit 6 of the instrument at address 1 is not high, then check the
instrument at address 7 to see if bit 6 of its status register is high.
6 As soon as the instrument with status bit 6 high is found check the
rest of the status bits to determine what is required.
The SPOLL(707) command causes much more to happen on the bus than
simply reading the register. This command clears the bus automatically,
addresses the talker and listener, sends SPE (serial poll enable) and SPD
(serial poll disable) bus commands, and reads the data. For more information
about serial poll, refer to your controller manual and programming language
reference manuals.
Status Reporting
Serial Poll
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