Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual - Manual (Page 102)

Programming Techniques
Chapter 7
7-5
In addition, the secondary 1785-BCM module compares the segment length
specified in the secondary program’s BTW instruction with the segment length
sent by the primary 1785-BCM module. If the segment lengths are different,
the secondary 1785-BCM module turns on the programming error bit (bit 3 is
local, bit 11 is remote).
Figure 7.2 shows how a program that uses the one-block-at-a-time method
works.
Figure 7.2
Program Flow for Transferring Data One Block at a Time
BTR
BTW
MAIN PROGRAM
DECIDE
PRI/SEC
RUN PRI
SUBROUTINE RUN SEC
SUBROUTINE
MOVE CRITICAL DATA
TO BTW FILE
CHECK BTR BLOCK ID
SET BTW BLOCK ID TO
EQUAL BTR BLOCK ID
MOVE BTW DATA
CHECK BTR BLOCK ID
MOVE BTR DATA
MOVE DATA TO FILE
PRIMARY
SECONDARY
11109I