Watlow Electric Revision 5 - Manual (Page 43)

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7.0 DETAILED MODULE DESCRIPTIONS
7.1 PROCESSOR I/O MODULE -- A32-PIOM
The PIOM is the main processor for the SYSTEM 32 and is required in each
system. The only PIOM option available for standard systems is the type of
communications interface.
The PIOM has two microprocessors, an 8031 and 8088. These microprocessors
perform all the SYSTEM 32 software operations using programs stored in
PROM's. The 8031 primarily manages the I/O functions including
communications, while the 8088 performs the control calculations including PID
and linearization thermocouple and other inputs. Other software functions include
self-test of the system, on-line analog calibration, and open heater detection.
The PIOM is comprised of a two board set, the larger board is the 8031 processor
and the smaller piggy back board is the 8088.
The SYSTEM 32 microprocessor programs allow control parameters and other
operating conditions, such as input types, to be entered from an external computer
through the built in serial interface. Communications protocol is a form of ANSI
X3.28-1976, which is compatible with Allen-Bradley PLC's.
Up to 29 parameters, such as input type, control setpoint, deviation alarms, PID
constants, can be entered for each loop. These parameters can be stored by
command in EEROM, and the SYSTEM 32 will start according to these
parameters on application of power or after a microprocessor reset.
WARNING: Only a safe set of parameters should be stored in
EEROM, since the system will automatically start with these values.
7.1.1 Control Outputs and Digital Inputs and Outputs
The standard SYSTEM 32 PIOM has 32 digital control outputs, 8 alarm and
status outputs, an additional 16 digital outputs, and 16 digital inputs.
In the simplest SYSTEM 32 configuration, the PIOM may be used without
any other modules as an open loop controller with 32 manually set control
outputs. The outputs can be set to any level [percent of full scale] from the
system computer.
When used for closed loop control, the 32 control outputs correspond to the
first 32 analog inputs. Additional analog inputs up to 96 total per PIOM,
are used for data acquisition. A special version of the SYSTEM 32 is
available for 48 control loops.
The control outputs may be independently software set as on/off, or pulsed
dc outputs with a choice of Cycle Time Proportioning or Distributed Zero
Crossing. The control action can be independently set for Reverse [Heat] or