HP 8153A, Руководство по эксплуатации и программированию

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6
SRQ, The Service Request
A service request (SRQ) is forced when a bit in the Status Byte register goes
from 0 ! 1 AND the corresponding Service Request Enable Mask bit is set.
If an SRQ is forced, the Request Service (RQS) bit is set to 1 . This bit remains
at 1 until read by a serial poll, even if the reason or condition that caused the
service request no longer exists . Similarly , if a serial poll reads the RQS it is
reset to 0 , even if the condition that caused the service request still exists . The
serial poll command transfers the value of the Status Byte register to a variable .
Input Queue
The input queue is a FIFO queue (rst-in rst-out) and is 1024 bytes long.
Output Queue
The output queue is a FIFO queue (rst-in rst-out) and is 274 bytes long.
The message available , Message A vailable (MA V), bit is set in bit four of the
Status Byte register whenever the output queue is not empty . Receiving a new
program message clears the output queue and the Message A vailable (MA V) bit.
This happens directly after the program message terminator is received.
Error Queue
The error queue is a FIFO queue (rst-in rst-out) and is 30 errors long. That is ,
the oldest error is the rst error to be read.
If the queue overows , message '-350 <too many errors>' overlays the last
message in the queue .
Remote Operation - Common Commands 6-3
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