PSI BOX PLUS+ Reference
Control Functions
SPE.
Sends Serial Poll Enable Command.
_____
_______________________________
Purpose.
Initiates a serial poll.
__________
The PSI BOX asserts ATN and becomes the active
controller, then the IEEE command SPE, hex 018h decimal 24,
is sent over the IEEE bus. After the command has been sent the
ATN remains true, PSI BOX is the active controller.
The SPE command is used automatically in the SPOLL
routine but it can be called separately to initiate your own serial
poll routine. If you have, say, two devices that can request
service, instead of serial polling them sequentially using SPOLL,
you may wish to poll them together. You would then use SPE as
part of your own routine. The SPE command can also be sent by
using CMD 24 or CMD 152
Format.
SPE
_________
Params.
None.
_________
Returns.
Only if used as part of a full serial poll sequence
__________
would a response from the IEEE bus be forthcoming.
Example.
________
_
BUS SPE
:REM ISSUE COMMAND
Bus Activity.
___________
_
assert ATN if not already so
SPE
Example.
________
_
A COMPLETE SERIAL POLL ROUTINE.
BUS SPE TALK 4 READ SPD UNT
BUS STATUS
:REM READ STRING
SP at position 11 :REM HOLDS REPLY.
Bus Activity.
___________
_
assert ATN if not already so
SPE
TAD 4
Page 144
Chapter 8
