Control Board
5-8 LigaSure Vessel Sealing Generator Service Manual
Audio Alarm
The audio alarm circuit resides on the footswitch board. Both software and
hardware control the audio alarm.
• The feedback microcontroller, in response to activation inputs, alarms, and
power-up, writes to a digital-to-analog converter (DAC) chip, U15, which
generates an analog control signal, V_FREQ. This signal provides software
control for the audio alarm. The V_FREQ signal connects from the control
board to the RF board through the 96-pin connector, and then from the RF
board to the footswitch board through the 20-pin footswitch ribbon connector.
• The RF_TONE\ signal provides hardware control. RF sensing circuitry on the
RF board generates the RF_TONE\ signal in the RF output stage.
Serial Interface
The RS-232 serial port is a software-polled interface to the main microcontroller
(U5). You can use it 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 serial port. The serial port configuration follows:
• 9600 baud
• 8 data bits
• 1 stop bit
• no parity
This timing is derived from the main microcontroller oscillator frequency of
11.0592 MHz.
The control board serial port signals connect to the RF board through the 96-pin
connector. The signals then connect to the 9-pin serial port connector on the RF
board.
Dosage Error Algorithm
The basis of the dosage error algorithm for the closed loop modes (bipolar and
seal) is a comparison between two microcontroller/sensor sets:
• Main microcontroller, current and voltage sensors
• Feedback microcontroller, current and voltage sensors
While the feedback microcontroller operates the generator, the master
microcontroller continuously monitors generator operation, calculating and
checking several values:
• Voltage and current input to the microcontrollers
• High voltage control signal
• High voltage sense signal
• Desired value (entered at the front panel) at the main microcontroller
• Desired value (entered at the front panel) at the feedback microcontroller
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