Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual User Manual
Page 70
Operating Your PLC-5 Backup System
Chapter 5
5-6
Figure 5.4
BTR Instruction Words
15
14
13
12
11
10
09
08
07
06
05
04
03
03
01
00
REMOTE STATUS
LOCAL STATUS
BLOCK IDENTIFICATION
62 WORDS OF DATA
(IN SECONDARY PROCESSOR ONLY)
Important: The lower byte of the status word is for the LOCAL status. These
bits indicate status of the 1785-BCM module installed in the same chassis as the
processor to which you are referring. The upper byte of the status word refers
to REMOTE status. Its bits indicate the status of the 1785-BCM module
installed in the other chassis of the backup system.
Word 1: System Status — Table 5.B lists the bits in the system status word and
defines each.
Table 5.B
System Status Word Bits (BTR)
Status
Bit
Description
0
Serial communication error; when on, this bit indicates a communication
error in the high speed serial link (HSSL)
1
I/O chassis backplane error; when on, this bit indicates a communication
error in the transfer of data from the PLC-5 processor to its 1785-BCM
module. Setting bits in the BCM output image table can set this bit.
2
Buffer full; if on, this bit indicates that the primary module cannot accept
writes, or it indicates that the secondary module has received a data block
before the first data segment has been read.
Local
3
Programming error; this bit is on when an out-of-range block is detected
between the primary 1785-BCM module and its PLC-5 processor. In the
secondary system, this bit is on when the transmitted segment length does
not match the received segment length.
If there is a BTW or BTR to the BCM module with an invalid length, the
module will not switch over, but this bit will not be on.
4
Remote I/O communication fault; when on, this bit indicates that a
communication fault exists on a remote I/O channel between the processor
and the 1785-BCM module. Refer to section “Auxiliary Diagnostics/Status
Words” to know which channel has a communication fault.
5
Reserved – Always 0
6
Primary/Secondary; when on, this bit indicates that the 1785-BCM module
belongs to the primary system; if off, the bit indicates that the module belongs
to the secondary system
7
Data valid; this bit is used only by the secondary processor. If the Fast
Data-Transfer mode is enabled, the bit is on when the 1785-BCM module
contains one data block available to be read. If the Fast Data-Transfer mode
is disabled, the bit is on when the 1785-BCM module contains one complete
segment.