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DESCRIPTION AND OPERATION
SERIAL CHANNELS
I-E96-202B
2 - 3
address it has. This section contains the latches whose
outputs connect to LEDs one through eight and the status
LED. Additionally this section contains an output that desig-
nates this module as the primary module. Upon a failover, this
output turns off and the backup module output energizes as it
takes over. This output actuates an LED that indicates which
module is the primary.
Additionally, the input and output section monitors the stop/
reset pushbutton. Pressing the pushbutton once causes this
section to bring the module to an orderly stop after completing
any input or output function currently in progress. Pressing
the pushbutton a second time resets the module.
SERIAL CHANNELS
The MFP module contains two independent, general purpose
serial channels. One use is for language support (C and
BASIC). Each channel supports standard baud rates up to
19.2 kilobaud. The appropriate termination unit or termination
module uses standard D-type connectors. The NTMP01,
NIMP01, or NIMP02 termination device optically isolates these
communication channels. This optical isolation eliminates the
need to tie chassis ground to system common and alleviates
the potential of damage from ground currents. One channel
can also be used as a RS-485 connection.
DMA SECTION
The microprocessor sets this section for direct memory access
or DMA. The DMA section allows data being received or trans-
mitted over the various communication paths to be transferred
directly to or from the RAM memory without microprocessor
intervention. This process is known as cycle stealing. It greatly
reduces the overhead associated with the microprocessor doing
such data moves. This circuitry is used for the higher speed
communication paths where the microprocessor would be
overloaded handling the data moves, specifically Controlway.
The 40-kilobaud station link and the redundancy link also use
this feature.
CONTROLWAY
The Controlway is the high-speed version of the module bus. It
provides a one-megabaud peer-to-peer communication link
capable of supporting up to 32 connections. The Controlway
interface is provided by a custom Bailey Controls integrated
circuit that links the MFP module to the Controlway. It has full
DMA capabilities (allowing for quicker operation), and two
redundant, independent communication channels.