Kongsberg Simrad IS12, Service Manual

Page: 36 / 67

Issue 1.0 09/06/03
SIMRAD
36
5 CIRCUIT DESCRIPTION
5.1 Square Display Unit PCB Assembly
Introduction. The PCB Assembly is a generic item which can be used for all square instrument
display units. The variants are created by applying different components, software versions and
hardware links to the common PCB. The various hardware options are detailed on the circuit
diagram Drawing No.
E03718 together with the appropriate assembly drawing. All displays employ
the same software, E04007, with the exception of the Mega Instrument, which employs E04251, in
position IC4. The table below gives a summary of the hardware links which select the appropriate
software option for the different displays:
Instrument Type Resistor / Link Fitting
Depth Display R100 R101 R102 R103 R104 R105 R11 R10
Speed Display R100 R101 R102 R103 R104
R12
R106
R10
Combi Display R100 R101 R102 R103 R104
R12 R11 R10
Data Display R100 R101 R102 R103
R13
R105 R106
R10
Mega Display R100 R101 R102 R103
R13 LK1
R106
R10
GPS Display R100 R101 R102
LK2 R13
R105 R106
R10
Wind Display R100 R101 R102 R14 R104 R105 R106 R10
Compass Display R100 R101 LK3 R14 R104 R105 R106 R10
Resistors numbered R100 to R106 are all valued at 10k_ and act as “pull-up” devices. Resistors
numbered R10 to R14 are all valued at 0 (zero) _ and act as “pull down” devices. Links LK1 to
LK3 provide additional pull down options to increase flexibility of board usage e.g. a Wind Display
can easily be converted to a Compass Display by making the solder link LK3.
NB. Post manufacturing changes to R100 to R106 and R10 to R14 are not recommended due to
their location between the PCB and the LCD.
Supply and Regulation . The Display Unit is designed to work from a 12 V source. Protection
against incorrect polarity is provided by D1. Capacitors C2 and C85 are used as reservoirs to hold
up the supply voltage and reduce any supply dips. Protection against over-voltage spikes is
provided by Resistor R1 and Zener Diode ZD1 and Regulator REG1 provide a 5V regulated
supply. Depth and Combi units require further supply input filters comprised of Inductors L4 to L7
and Capacitors C99 to C102 to suppress emissions due to the high energy depth transmitter pulse.
Microprocessor . The Microprocessor has 60 Kbytes of ROM, for program storage, 2 Kbytes of
RAM for temporary variable storage and is equipped with a CAN (Controller Area Network)
module.
The Microprocessor is driven at 9.83040 MHz by Crystal XTAL1 connected to Pin 12 (Xin) and Pin
13 (Xout). Capacitors C13 and C14 form the load and integrated reset generator IC3 provides a
reset LOW pulse of approximately 50mS duration at switch on and whenever a 5v supply failure
occurs. In addition to the reset provided by IC3, the microprocessor has a built in watchdog timer
which will create a reset if a software crash occurs for any reason.