Rockwell Automation 1771-IJ_IK IK ENCODER/COUNTER MODULES - Manual (Page 52)

6–8 Block Transfer Programming
Publication 1771ĆUM006B-EN-P - June 2002
Figure 6.6
Sample Ladder Logic for PLCĆ3 Block Transfer
LE
BTW
DN
ER
XOR
A XOR B = R
A : WB001:0030
B : WB001:0030
R : WB001:0030 XOR
A XOR B = R
A : WB001:0020
B : WB001:0020
R : WB001:0020 S0003
03
EQU
A : WB001:0030
B : WB001:0020
WB001:0020
15
A = B
CNTL
02
CNTL
05
CNTL
03
LE
DN
ER
CNTL
12
CNTL
15
CNTL
13
WB001:0030
05
RUNG NUMBER RM1
RUNG NUMBER RM2
RUNG NUMBER RM3
1
2
3
15064
BLOCK XFER WRITE
RACK :
GROUP :
MODULE :
DATA:
LENGTH =
CNTL:
002
1
1 = HIGH
FB002:0150
0
FB001:0030
BTR
BLOCK XFER READ
RACK :
GROUP :
MODULE :
DATA:
LENGTH =
CNTL:
002
1
1 = HIGH
FB002:0220
0
FB001:0020
Rung Descriptions
Rung 1 - Rung one is true only at power up. It uses status word 3,
bit 03 (the PLC-3’s AC power loss bit) to zero the control file of both
the BTR and BTW instructions.
Rung 2 - The equal instruction is used at power up. At power up, the
BTR and BTW control files both equal zero, so the BTW instruction
is enabled.
Rung 2 and 3 - During normal program execution, the BTW and
BTR instructions are alternately executed. The done bit of either
instruction enables the next block transfer instruction. After power
up, the BTR and BTW done bits are used to alternate reads and
writes.