
DESCRIPTION AND OPERATION
COMMUNICATION
I-E96-213A
2 - 3
Module Bus
The module bus provides an 83.3 kilobaud peer-to-peer com-
munication link capable of supporting up to 32 drops. The
module bus interface is provided by a custom Bailey Controls
integrated circuit, that interfaces the MFC to the module bus.
Redundancy Link
The redundancy link is a 25 kilobit serial link between a pri-
mary and backup MFC in redundant configurations. As the
primary module executes, the backup module waits in hot
standby mode and receives a copy of all block outputs over this
link. If for any reason, the primary module fails, the backup
module takes over immediately without any process
interruption.
Station Link
Station link controls the serial communication between the
MFC and the panel stations. It has two modes of operation.
When used with the Control Station (IISAC01), it provides a 5
kilobaud serial channel for up to eight stations. This link con-
nects to the termination unit or termination module for control
stations via the NTMF01 or NIMF01 and the cable NKSE01.
COMMUNICATION
The IMMFC05 has four communication channels (module bus,
slave expander bus, Control Station Link, Redundancy Link).
Through the module bus, the MFC can communicate with
other control modules in its process control unit (PCU). The
slave expander bus is an 8 bit parallel bus located on the MMU
backplane. It provides the path for bidirectional communica-
tions with slave modules. This bus, through a 12 position dip-
shunt, can be broken to create separate busses for different
masters. The Control Station Link allows the MFC to commu-
nicate with a Control Station. The Redundancy Link allows
communication between a primary MFC and a backup MFC.
Data Transfer on Slave Expander Bus
Data transfer between the MFC and its slaves occurs on the
slave expander bus. The MFC can execute four types of data
transfer functions. They are: write a command to a slave,
request a slave status, write data to a slave, and read data from
a slave.
The MFC always initiates the data transfer operation. When a
data transaction occurs, the MFC addresses a slave, requests
the information, and reads or writes the data.