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CHAPTER 5: Command Descriptions
MODE
CA
BUS STATES
ATNUNL, MLA, TAG, UNL,TCT, *ATN
EXAMPLES:
100
PRINT#1,"PASS CONTROL 22"
Control is passed to device 22.
110
PRINT#1,"STATUS 1"
Wait until we are controller again.
120
INPUT#1,A$
130
IF LEFT$(A$,1)<>"C" THEN 110
Use STATUS 1 to check
140
<rest of program>
The next example uses the ARM command to determine when control been given back to the 488
Controller.
100
PRINT#1,"PA 22"
Control is passed to device 22.
110
PRINT#1,"ARM CO"
120
INPUT#1,A$
Wait until we are controller
130
<rest of program>
PPOLL Command
The Parallel Poll command, PPOLL, is used to request status information from many bus devices
simultaneously. If a device requires service then it will respond to a Parallel Poll by asserting one of the eight
IEEE bus data lines (DIO1 through DIO8, with DIO1 being the least significant). In this manner, up to eight
devices may simultaneously be polled by the controller. More than one device can share any particular DIO
line. In this case it is necessary to perform further Serial Polling to determine which device actually requires
service.
Parallel polling is often used upon detection of a Service Request (SRQ), though it may also be performed
periodically by the controller. In either case, PPOLL will respond with a number from 0 to 255
corresponding to the eight binary DIO lines.
Not every device supports parallel polling. Refer to the manufacturer’s documentation for each bus device
to determine if Parallel Poll capabilities are supported.
SYNTAX
PPOLL
RESPONSE
Number in the range of 0 to 255
MODE
CA
BUS STATES
ATNEOI,<parallel poll response>, *EOI
EXAMPLE:
PRINT#1 "PPOLL"
Conduct a Parallel Poll
INPUT#1,PPSTAT
Receive the PPOLL status
PRINT PPSTAT
