Service manual

Revision D 4-13
Troubleshooting : Control PCB Theory
Series 2000 Treadmill
409110-004
Control PCB Theory
General Description
The 800320-001 control board and the 800334-002 power board
function together to control the Series 2000 Treadmill. The control
board contains the following:
■
Micro-controller CPU circuitry (78310)
■
Memory (EEROM code/calibration/history data, SRAM)
■
Temperature sensor
■
Speaker driver
■
Some of the I/O circuitry
The I/O circuity receives inputs from a stress system controller along
with feedback from the treadmill sensors to control the elevation and
drive systems located on the 800334-002 power board.
Power Distribution
The control board receives 5 volts of power from the power board.
Bypass caps distributed across the board minimize EMI and power
supply noise. Other analog supplies are created from the 5-volt supply
to the board with voltage doublers.
Clock Generator
A 12 MHz crystal provides the processor clock. Sharp clock edges are
controlled by the 100-ohm series termination resistors to minimize EMI.
Reset Generator
The Reset/Watchdog generator resets the CPU under any one of three
conditions:
■
Upon receipt of a “BREAK” signal over the RS-422 port, the 100
K/0.33µF RC will discharge, creating the PBRESET* and RESET*
signal.
■
If the 5 V (±5%) supply falls below 4.5 V, RESET* is activated.
■
If the CPU fails to reset the watchdog timer for 1.2 seconds, the
RESET* is activated. The software has the watchdog control
software “threaded” through its task-switcher to help guarantee
that all processor tasks are running.