PSI BOX PLUS+ Reference
Control Functions
SPOLL.
Perform A Complete Serial Poll.
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_
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Purpose.
To determine which device has requested service
__________
from the controller and why.
The SERIAL POLL is usually called after a device asserts
SERVICE REQUEST by setting SRQ low. Serial poll is the
only method that can correctly cause the device to return the
SRQ line false. In general, you will know which device
requested the service and so will know which to poll. However,
if it could be one of several devices that is requesting service,
you should perform successive serial polls on the different
devices until the SRQ line returns to the false state.
NOTE:
It is the IEEE device that causes the serial poll to be
performed because it asserts SRQ when it needs
servicing by the controller.
Format.
SPOLL serially polls the currently addressed device.
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The serial poll response is stored in bytes 28-30, the
current device serial poll data, and in bytes 32-34,
the first addressed device serial poll data, in the IEEE
control status string.
6,SPOLL makes device 6 the current device, then
serially polls the currently addressed device.
SPOLL 6,7,8 serially polls the three devices 6,7 and
8 one after another. The serial poll response of each
device is held in bytes 28-30 of the IEEE control
status string when that device is addressed as the
current device. The serial poll response for device 6
is placed in bytes 32-34, the serial poll data of the
first addressed device.
Params.
None, One or Some.
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Returns.
The serial poll response contains data concerning the
__________
service request.
it 6 (value 64) set if it was the device requesting
service, if so then the other bits will contain a code
indicating the nature of the service requested.
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Chapter 8
