ASCII Module
PLC-2 Family Processors
Appendix A
A38
Program the read and write block transfer instructions of your ASCII
module in the same rung (Figure A.16).
Distribute your block transfer modules equally between all four scanner
channels.
Distribute block transfer instructions equally throughout your program.
Place an equal number of non–block transfer rungs between block
transfer rungs.
For large numbers of block transfer instructions, distribute groups of
block transfer rungs equally throughout your program. Place no more
than four block transfer rungs consecutively in one group. Within each
group, condition the next rung using the done bit of the previous block
transfer instruction.
Consider an additional I/O scanner module (cat. no. 1775–S4A) if you
cannot otherwise reduce the block transfer times to meet your timing
requirements.
During a write handshake, the processor also can transfer write data to
the ASCII module; and during a read handshake, the processor also can
transfer read data.
Figure A.16
Example Block Transfer Programming
WB001:0000
15
WB001:0000
05
BTR
BLOCK XFER READ
RACK :
GROUP :
MODULE:
DATA :
LENGTH =
CNTL:
001
1
1 = HIGH
FI001:0005
0
FB001:0000
CNTL
12
EN
CNTL
15
DN
CNTL
13
ER
WB001:0000
17
BTW
BLOCK XFER WRITE
RACK :
GROUP :
MODULE:
DATA :
LENGTH =
CNTL:
001
1
1 = HIGH
FO001:0004
0
FB001:0000
CNTL
02
EN
CNTL
05
DN
CNTL
03
ER
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