Issue 1.1 18/07/03 SIMRAD
20
LCD operation. Oscillation for the negative voltage generator is provided by circuitry associated
with IC8a.
Microprocessor. The microprocessor reads the key matrix S1 to S9 directly, gives the relevant
commands to the LCD and the Bus and provides drive signals to the back-light via TR1 and to the
buzzer via TR2.
EMC. A variety of measures are included in the circuit to limit the susceptibility of the circuit to
interference and to provide reduction of emissions. Extensive de-coupling of the microprocessor
I / O lines is carried out using 100pF capacitors.
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