Control Board
Principles of Operation
Force FX-8C Service Manual 4-9
Each code generates a unique waveform pattern to be delivered to the RF
output stage of the generator. The T_ON ASIC reads and evaluates the
code and, if the code value is acceptable, repetitively generates the
appropriate waveform until the activation request ends. After the request
ends, the feedback microcontroller places the T_ON ASIC back into reset.
If the code received by the T_ON ASIC is not valid, the internal program
sets an error flag, deactivates all output signals, and remains in an error
state until the system is reset.
T_ON Average Check
The T_ON waveform generator output waveform is integrated in
hardware and returned to the main microcontroller as an analog value
called T_ON average. The T_ON average is different for each distinct
output mode of the T_ON waveform generator. The main microcontroller
continually checks the T_ON average for compliance with the calibrated
value to ensure that the T_ON waveform generator is operating properly.
The T_ON average signal rests at 5 V when the generator is not activated
and drops to the calibrated value when activation occurs. The main
microcontroller checks to make sure the T_ON average signal is within
± 15 counts of the calibrated value.
During wak control in the coag modes, the T_ON average rises an
indeterminate amount. Due to this unknown, the T_ON average is
allowed to rise to 253 counts, which guarantees the T_ON waveform
generator is still operating. The T_ON average is still not allowed to drop
below the lower limit of 15 counts mentioned above.
Audio Alarm
The audio alarm circuit is located on the Footswitch board. The audio
alarm is controlled by software and hardware.
• Software control is provided by the UP_TONE\ (microcontroller tone)
and LO_TONE signals generated by the main microcontroller in
response to activation inputs, alarms, and at power-up. These signals
connect from the Control board to the Power Supply/RF board
through the 96-pin connector and then from the Power Supply/RF
board to the Footswitch board through the 16-pin footswitch ribbon
connector.
• Hardware control is provided by the RF_TONE\ signal generated in
the RF output stage by RF sensing circuitry on the Power Supply/RF
board.
Serial Interface
The RS-232 serial port is a software-polled interface to the main
microcontroller (U5). It is used for diagnostics and calibration.
Transmission and receipt of command strings do not stop real time
processing, except as single characters are read from or written to the
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