Processor Circuitry; Analog Inputs; Rs-232/422 Interfaces - GE T2100 Service Manual

Processor Circuitry

Analog Inputs

Ratiometric Inputs
Temperature Sensor

RS-232/422 Interfaces

5-12
Theory of Operation: Processor Board (PCB) Theory
The MC9s12DG128 runs at 16 MHz with an internal bus clock of 8 MHz.
Its code is stored in the 128 KB Flash EPROM. The MC9s12DG128
addresses its memory internally. The processor handles all the I/O,
including two serial channels, 4 analog inputs, and digital inputs and
outputs to control the GE T2100 Treadmill grade, speed, calibration and
ESTOP processes.
Elevation feedback (from the pot), +5.1V ISO ref, VUNREG ref are
designed to take ratiometric voltages referenced to +5.1V ISO as inputs
to the processor.
The processor monitors temperature and saves peak temperature in
EEROM data storage for use by field service. The sensor outputs 10mV/
deg C. The OPAMP provides a gain of 4.92. The MC9s12DG128 ADC will
produce the following output:
In hardware
!
ADC value = Temp(deg C) * 10mV/deg C * GAIN * [256(max ADC
"
counts)/VREF]
In firmware
!
Readout temp = (ADC value) * 4 / 10
"
For example:
"
At 25 degrees Celsius
ADC value = 25 * 0.01 * 4.92 * 256 * /5.1 = 62 (Dec)
Readout temp = 62 * 4 / 10 = 24.8
At 100 degrees Celsius
ADC value = 100 * 0.01 * 4.92 * 256 * /5.1 = 247 (Dec)
Readout temp = 247 * 4 / 10 = 98.8
The LTC1334 serves as the Host to IFC board transceiver. It translates
the RS422/232 serial protocol voltage levels to TTL levels. The MAX489
is the transceiver for the processor board to drive communication. It
translates RS422 signals to proper TTL levels.
GE T2100 Treadmill
2021403-031
Revision A