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3-1-2 Operation via WRIT(87)/READ(88)
When pin 2 of the back panel DIP switch is ON, data can be transferred to and
from the Ladder Program I/O Unit using the I/O WRITE and I/O READ
(WRIT(87)/READ(88)) instructions from the PC. WRIT(87) and READ(88) are
used automatically for this data transfer in the Ladder Program I/O Unit and are
not available for user programming except in the PC. The Ladder Program I/O
Unit must be mounted to the CPU Rack or Expansion I/O Rack of a PC that sup-
ports WRIT(87)/READ(88).
Data written by the WRIT(87) instruction in the PC program is stored in DM 064
through DM 095 in the Unit. A maximum of 32 words can be transferred. Data
read by the READ(88) instruction in the PC is stored in DM 096 through DM 127.
A maximum of 32 words of data can be read. The bits in parentheses are con-
trolled automatically (as described below) when WRIT(87)/READ(88) are en-
abled. Treat these as read-only bits. The other input and output bits shown be-
low can be used as normal I/O bits.
Do not output to word n with the MOV(21) instruction in the PC program. When
outputting to word n, set the PC Busy, PC Write Completed, and PC Read Com-
pleted Flags to 0 (OFF). Also, do not output to word 01 with the MOV(21) instruc-
tion in the Ladder Program I/O Unit program. When outputting to word 01, set the
I/O Busy, I/O Read End, I/O Write End, I/O Read OK, and I/O Write OK Flags to 0
(OFF).
Bit 0103 (the I/O Read OK Flag) is turned ON when data has been transferred
correctly with the WRIT(87) instruction. It remains ON until the WRIT(87) in-
struction is executed again. Bit 0104 (the I/O Write OK Flag) is turned ON when
data has been written from the Ladder Program I/O Unit. It is turned OFF when
the READ(88) instruction is executed in the PC.
PC Word Allocation
Unit Word Allocation
Bit No.
IR n
IR n+1
Bit No.
Word 00
Word 01
Output
Input
Input
Output
00
(PC Busy)
(I/O Busy)
00
(PC Busy)
(I/O Busy)
01
(PC Write
Complete)
(I/O Read
End)
01
(PC Write
Complete)
(I/O Read
End)
02
(PC Read
Complete)
(I/O Write
End)
02
(PC Read
Complete)
(I/O Write
End)
03
Output bit 03
(I/O Read Ok)
03
Input bit 03
(I/O Read Ok)
04
Output bit 04
(I/O Write Ok)
04
Input bit 04
(I/O Write Ok)
05
Output bit 05
Input bit 05
05
Input bit 05
Output bit 05
06
Output bit 06
Input bit 06
06
Input bit 06
Output bit 06
07
Output bit 07
Input bit 07
07
Input bit 07
Output bit 07
08
Output bit 08
Input bit 08
08
Input bit 08
Output bit 08
09
Output bit 09
Input bit 09
09
Input bit 09
Output bit 09
10
Output bit 10
Input bit 10
10
Input bit 10
Output bit 10
11
Output bit 11
Input bit 11
11
Input bit 11
Output bit 11
12
Output bit 12
Input bit 12
12
Input bit 12
Output bit 12
13
Output bit 13
Input bit 13
13
Input bit 13
Output bit 13
14
Output bit 14
Input bit 14
14
Input bit 14
Output bit 14
15
Output bit 15
Input bit 15
15
Input bit 15
Output bit 15
"# $" #% &
Section 3-1
Summary of Contents for C500-LDP01-V1
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