GE T2100, Service Manual

Page: 61 / 152

Revision A GE T2100 Treadmill 5-11
2021403-031
Theory of Operation: Processor Board (PCB) Theory
Processor Board (PCB) Theory
General Description
The processor board and power board function together to control the GE
T2100 Treadmill. The processor board contains the following:
"
Micro-controller CPU circuitry (MC9S12DG128)
"
Flash Memory (calibration/history data)
"
Temperature sensor
"
Serial control links
"
I/O circuitry
The I/O circuitry receive inputs from a stress system controller along
with feedback from the GE T2100 Treadmill sensors to control the
elevation and drive relays located on the power board.
Power Distribution
The processor board receives two sources of 5-volt power from the power
board: an isolated supply, and a non-isolated supply. Bypass caps
distributed across the board minimize EMI and power supply noise.
Clock Generator
A 16.00 MHz oscillator in a colpitts configuration is used to provide the
processor clock. This configuration creates a small amplitude (1 Vp-p)
sinusoid mounted on a DC bias level to minimize EMI.
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.