DESCRIPTION AND OPERATION
FUNCTIONAL OPERATION
WBPEEUI240756A0 2 - 3
Microprocessor and Control Logic Circuitry
The on-board microprocessor and control logic coordinates
module functions. The microprocessor has four main
functions:
•
Storing the digital data in random access memory (RAM).
•
Coordinating analog-to-digital conversion through the ana-
log-to-digital control chip.
•
Preparing digital commands to send to the smart
transmitters (IMFEC11 only).
•
Reading and sending data to the controlling module (MFP/
MFC).
The microprocessor directly links to eight kilobytes of random
access memory. This memory serves as a storage area for pro-
cess data and transmitter configuration information.
The microprocessor coordinates analog-to-digital conversions
through ADC circuitry. The microprocessor takes the con-
verted process data it receives from the ADC circuitry and
places it into a memory buffer. It remains in memory until the
controlling module makes a request for process data or the
microprocessor updates it with a new value. When the micro-
processor receives a request for process data, it transfers that
data from the memory buffer to a first in first out (FIFO) shift
register where the controlling module can access it through the
I/O expander bus interface.
For IMFEC11 modules (FSK communications), the micropro-
cessor sends command signals to the transmitters through the
module communication circuitry. The circuitry converts com-
mands from the microprocessor into FSK signals. The micro-
processor directs the command transmission to the proper
channel.
The MFP module communicates with the FEC module over the
I/O expander bus. An Elsag Bailey designed integrated circuit
interfaces the microprocessor to the I/O expander bus. All
MFP commands and process data pass through the I/O
expander bus interface and first in first out inputs or outputs.
Module Input/Output Circuitry
Process inputs to the IMFEC11/12 modules can be standard
analog signals of four to 20 milliamps and ±10 VDC; or analog
(point-to-point) or frequency shift keyed digital signals (on a
field bus) (IMFEC11). The module input circuit provides two
paths for process data inputs. One path handles standard ana-
log inputs and analog point-to-point inputs. The other path
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