Rockwell Automation 1785-BCM_BEM, D17856.5.4 PLC-5 Backup Communication Module User Manual - Manual (Page 71)

Operating Your PLC-5 Backup System
Chapter 5
5-7
Status Description Bit
8 Serial communication error; when on, this bit indicates a communication
error in the high speed serial link (HSSL)
9 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. See bit 1.
10 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.
Remote
11 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. See bit 3.
12 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.
13 Processor fault; when on, the bit indicates that the local system detects a
failure in the remote processor or the remote processor is in PROGRAM
mode
14 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
15 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.
Important: If the fault is cleared and a successful BTR is executed, the five
least significant bits (00, 01, 02, 03, 04) are automatically turned off.
Word 2: Block Identification (Block ID) — Word 2 of the BTR is the block
identification word (block ID). Its meaning varies depending on whether it is
the primary or secondary system.
In the primary system, word 2 of the BTR instruction indicates the number of
the next block to be sent. To calculate this number, the 1785-BCM module
adds 1 to the block ID number of the last block that was successfully transferred
from the PLC-5 processor to the module through a BTW instruction. If the
block is not received successfully, the 1785-BCM module does not increment
the last block number. It, however, returns the number of the block in error so
that the block can be automatically re-transmitted.