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Chapter 6. Service Request Function
6.5 SVC_REQ 4: Change Backplane Communications Window
Mode and Timer Value
Use SVC_REQ 4 to change the Backplane Communications window mode and timer value. The
change takes place during the next CPU sweep after the function is called.
SVC_REQ 4 executes unless a mode other than 0 (Limited) or 2 (Run to Completion) is selected.
The parameter block has a length of one word.
6.5.1
To disable the Backplane Communications window:
Enter SVC_REQ 4 with this parameter block:
Address High Byte Low Byte
Address
0
6.5.2
To enable the Backplane Communications window mode:
Enter SVC_REQ 4 with this parameter block:
Address High Byte
Address Mode
0 = Limited
2 = Run to Completion
SVC_REQ 4 Example
When enabling output %M0125 transitions on, the mode and timer value of the Backplane
Communications window is read. If the timer value is greater than or equal to 25ms, the value is not
changed. If it is less than 25ms, the value is changed to 25ms. In either case, when the rung
completes execution the window is enabled. The parameter block for all three windows is at location
%R5051. Since the mode and timer for the Backplane Communications window is the second value
in the parameter block returned from the Read Window Values function (SVC_REQ 2), the location of
the existing window time for the Backplane Communications window is in the low byte of %R5052.
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PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
0
Low Byte
1ms value 255ms
GFK-2950C
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