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SeaTalk Service Manual
2
1. Course Computer PCB Circuit Description;-
Circuit diagram Fig. 1.
PCB assembly/parts list Fig. 2.
1.1. Power Supplies
Incoming power is routed to the PCB via the 'D' connector plug PL1. VI provides
suppression against any voltage spikes present on the incoming DC supply whilst D6
protects against reverse connection of the supply. 1C 1 is a 5V regulator and can
also reset the microprocessor, via TR9, should the supply voltage fall below 6V.
TR17, C19, D13, R92 and R91 form an 8V regulator to supply the windvane.
1.2. Microprocessor and Program Memory
IC2 is an Intel 80C32 microprocessor. It can access up to 32k bytes of program
memory (IC7) via the latch IC6. A clock signal for the microprocessor is provided by
an 11 MHz ceramic resonator (XL1) and associated capacitors C15 and C16. C14,
18 and 17 provide decoupling.
1.3. Analogue to Digital Converter
IC3,4,5 and 9 form a software driven analogue to digital converter. IC3 and IC9 are 8
channel multiplexed analogue switches routing all analogue signals, (see table
below), through to IC4 which is configured as an integrator. C9 is discharged at a
constant rate triggering the comparator IC5 as it reaches a level of approximately
0.53V. The output of the comparator is connected to the microprocessor thus
measuring the discharge time which is proportional to the analogue input.
Analogue Channels;-
IC3 Channel 0 Reset integrator
Channel 1 Integrator discharge signal
Channel 2 Fluxgate sense A
Channel 3 Fluxgate sense B
Channel 4 Motor Feedback 1
Channel 5 Motor Feedback 2
Channel 6 Windvane sense 1
Channel 7 Windvane sense 2
IC9 Channel 0 Alarm sense 1
Channel 1 Alarm sense 2
Channel 2 Rudder Reference
Channel 3 Supply Monitor
Channel 4 Rate Gyro sense
Channel 5 Gyro Compass sense
Channel 6 Joystick
Channel 7 Not used
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