Sailor RE2100, Technical Manual

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5 CIRCUIT DESCRIPTION AND SCHEMATIC DIAGRAMS RE2100
TUNE/ALARM TONE GENERATOR
Tune and alarm tones are generated in the microprocessor and sent out in P26.
Tune tones consist of two simultaneous frequencies of 1000 Hz and 2000 Hz. The microprocessor
generates a signal of 2000 Hz. A divider (1/2 U02), enabled by P54, divides the signal to 1000 Hz, and
the transistor Q01 adds the two signals before they are passed on to the exciter unit (module 4).
The alarm tones consist of two changing frequencies of 1300 Hz and 2200 Hz. Both tones are generated
in the microprocessor. The divider (1/2 U02) will be disabled.
DISTRESS DRIVER
When a distress frequency (2182 kHz) is selected, the microprocessor port P20 goes high and Q03 will
be able to source up to 14 mA. The distress signal is used when connection is made to SAILOR scrambler
CRY2001 or CRY2002.
SERIAL PERIPHERAL INTERFACE BUS (SPI)
The SPI-Bus is a synchronous serial bus supplying the other units with data. The clock speed is 38.5 kHz.
Through 4 drivers in U10, the clock and data are passed on to the modules which are connected to the
SPI-bus. The strobes for the various modules are generated in SPI address select U09. Through the 4
ports of the microprocessor, P60 - P63, an address is set up, which is suitable for the module which is
going to receive the serial data.
BAUD RATE GENERATOR
The baud rate generator U01 and 1/2 U02 divide the internal clock frequency of 2 MHz by 26 by means
of a duty cycle of 50 per cent. The divided frequency is equal to the frequency which must be added to
the internal serial communication interface (SCI) of the microprocessor, so that the baud rate of the SP-
Bus will be 4800 baud.
SP-BUS TRANSMITTER AND RECEIVER
The communication from and to the RE2100 is time multiplexed data bus. It is implemented with a 50 ohm
coaxial cable, terminated in both ends, and a transmitter and a receiver in each connected unit.
The RE2100 is the master and a number of slaves may be connected to the SP-Bus. When a slave (except
from T2130) wants to be called, the slave sends an interrupt to RE2100 on the SP-Bus INTERRUPT. The
transmitter and the receiver are identical in each unit connected to the SP-Bus. The transmitter output is
normally in high impedance state except when transmitting on the SP-Bus. The transmitter consists of
two gates, U13/1 and U13/2 (74HC00), a transistor Q04 (BC558) for level shifting, and two complemen-
tary output transistors Q05 (BC640) and Q06 (BC639). The transmitter is connected to the microproces-
sor P24 (Transmit Data), and P55 (Transmitter Enable).
The receiver consists of an op-amp, (U12/1, MC1458) which is configurated as a Schmitt Trigger and two
diodes D04 and D11 for level conditioning. The receiver is connected to the microprocessor P23 (Receive
Data). As the levels on the SP-Bus approximately match the RS232C standard, it is possible to connect
an RS232C to the SP-Bus. The cable terminations (jumper P04) must be removed when the external
RS232C is to transmit on the bus.
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