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Theory of Operation
Reset Generator
The reset/watchdog/power-loss signal generator will reset the CPU if any of the five
conditions below occur:
1.
Upon receipt of the "BREAK" signal for more than 3.3 seconds over the host
serial port, the 100K/0.33uF RC will discharge sending a low level at the MR*
input and creating the RESET* signal.
2.
If the 5V (+/- 2%) supply falls below 4.55, RESET* will be activated.
3.
If the CPU fails to reset the watchdog timer before 1.6 seconds, the RESET* will
be activated. The Firmware has the watchdog control task separated form
the other systems tasks through its real time operating system (RTOS) to help
guarantee that all tasks are running.
4.
If the ESTOP plug is disconnected from the jack mounted on the processor board
a RESET* signal will be generated.
5.
Manual reset.
Processor Circuitry
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 T2100 Treadmill grade, speed,
calibration and ESTOP processes.
Analog Inputs
Ratiometric Inputs
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.
Temperature Sensor
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
64
T2100 Treadmill
2021403-120F
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Troubleshooting
