
DESCRIPTION AND OPERATION
MODULE DESCRIPTION
2 - 2
I-E96-213A
®
Clock/Timer
The Clock section provides the clock signals to drive the mod-
ule at 12 Megahertz. Additionally, it supplies the lower fre-
quency clock signals for the module's system timer for uniform
control algorithm execution. All clocks originate from the 48
Megahertz oscillator on the module.
Memory
There are 128 kilobytes of ROM, 128 kilobytes of RAM and 64
kilobytes of battery-backed RAM. The ROM holds the operating
system instructions for the processor. The RAM provides tem-
porary storage and a copy of the user's configuration. The bat-
tery-backed RAM (BATRAM) holds the user's configuration
(control strategy designed with function codes). It is unique in
that it retains whatever information it has even when power is
lost. This is possible because of the backup batteries that keep
the memory active if power is lost.
Slave Expander Bus
The slave expander bus resides on the backplane of the module
mounting unit. It is an eight bit parallel bus that provides the
communication path for I/O data from slave modules. It can
support up to 64 low power slaves (both Network 90 and INFI
90). The bus uses Bailey Controls designed protocol to ensure
data integrity. The bus bandwidth is 500 kilobytes per second.
I/O Section
The I/O Section interface allows the processor to read the
switches that tell it how to operate and set its address. The I/O
section contains the latches whose outputs connect to the sta-
tus and error LEDs. An additional function contained in this
section is an output that shows that a master is operating as
the primary. Upon a failover, this output de-energizes and the
backup's output energizes as it takes over. The termination
unit or termination module uses this output to show the cur-
rent master.
Additionally, the I/O section monitors the Stop and Reset
pushbuttons. When you press the Stop pushbutton, this sec-
tion ensures that the module completes any I/O functions
before it brings the module to an orderly stop. When you press
the Reset pushbutton, the module restarts after the processor
and support circuitry is reset.