2-8 Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide May 2000 GFK-1527A
2
LEDs
Connector for
Programmer
Connector for
Redundancy
Communica tions
or Bus Receiver
Module
MODULE OK
PROGRAMMER PORT EN A BL ED
EXPANSION PORT ENAB LED
(Programmer Port)
(Expansion Port)
Bus Transmitter Module
A Bus Transmitter Module (BTM), catalog number IC697BEM713 or IC687BEM713 (½ slot
version), must be in rack 0 of both th e Primary PLC and the Secondary PLC in a Hot S t andby CPU
Redundancy system. The Bus Transmitter Module provides a path for Redundancy
communications when connected to the Redundancy Communications Module as described
previously. Each PLC in the redundancy system (Primary and Secondary) must have a BTM and
an RCM in rack 0.
C
P
U
B
T
M
R
C
M
31
Primary Unit Secondary Unit
30
P
SP
S
B
T
M
R
C
M
Redundancy Communications Link
Redundancy Communications Link
G
B
C
G
B
C
C
P
U
( RACK 0 ) ( RACK 0 )
When included as a bus communications module in an I/O expansion system, the BTM is a high
speed parallel interface wh i ch propagates the I/O bus signal s thr ough a cable to a Bus Receiver
Module located in the first I/O expansion rack. The BTM also provides a high speed parallel
connection to the programmer.
Connectors
The lower connector on the BTM is used t o connect to a
Redundancy Communications Module in the other
Redundancy system or to a Bus Recei ver Module in the first
expansion rack. Standard parallel I/O cables are used to
make the connection to a Bus Receiver Module. Cables with
built-in termination are used to make the connection to a
Redundancy Communications Module.
The upper connector provides a parallel connection to a Work
Station Interface (WSI) board installed in the programmer for
the Series 90-70 PLC.

Bus Transmitter Module S tatus LEDs

Module OK: The top LED is ON when the CPU software has
completed its power-up configuration of the BTM, and has
polled (or attempted to poll) each expansion rack in the
system. It is OFF when any of these conditions are not met.
Programmer Port Enabled: The middle LED is either blinking
or ON when the programmer and th e PLC are
communicating. It is OFF when they are not communicating.
Expansion Port Enabled: The bottom LED shows the status of
the expansion bus. This LED i s ei th er blinking or ON when
the BTM is communicating.