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5. Perform the Expansion Instruction Function Code Assignment operation to
assign a function code to XDMR(––).
6. Input the program.
The following program changes the Special I/O Unit Area settings for Unit 2,
restarts the Unit, and disables calculations using data from Unit 2 while the Unit
is initializing.
@XDMR
#0100
#8200
DM1200
DIFU(13) AR0102
JMP(04) 00
JME(05) 00
Unit #2 Restart Flag
Disables
calculations
during Ini-
tialization.
Calculations using data from Special I/O Unit 2
Transfers
the contents
of DM 8200
through
DM 8299 to
DM 1200
through
DM 1299.
End of process 1.
Restarts
Unit 2.
40000
27402
4-12-4 Special I/O Unit I/O Refreshing Interval
When the interval between I/O refreshes is too short, the processing in the Spe-
cial I/O Unit can be delayed causing Special I/O Unit errors or otherwise interfer-
ing with proper Unit operation. In this case, use the following methods to restore
normal operation.
There are two ways to extend the interval between I/O refreshes. Either of these
methods can be used.
1, 2, 3... 1. Disable cyclic Special I/O Unit refreshing in the PC Setup (DM 6621) and
use IORF(97) to refresh the Special I/O Unit’s I/O only when necessary.
To disable cyclic refreshing for all Special I/O Units mounted to the CPU
Rack or Expansion I/O Racks, set DM 6621 to #0100.
2. Increase the PC’s cycle time by setting a minimum cycle time in the PC
Setup (DM 6619) or executing SCAN(18) in the program. (SCAN(18) is an
expansion instruction with default function code 18.)
Change the program to use either IORF(97) refreshing or END refreshing. It is
also possible to increase the PC’s cycle time by setting a minimum cycle time in
the PC Setup (DM 6619) or executing SCAN(18) in the program.
Change the program to increase the spacing between IORF(97) instructions or
use just one IORF(97) instruction.
Example Program
(Special I/O Unit 2)
Short Interval between
END Refreshes
Short Interval between
IORF(97) and END Refresh
Short Interval between
IORF(97) Instructions
Special I/O Unit Interface Programs Section 4-12