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Comtech EF Data C5 User Manual

Page 214

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Theory of Operation

C5/K1/K3 Integrated Satellite Terminal System

5-4

Rev. 0

The non-volatile RAM on the M&C module allows the module to retain configuration
information without prime power for 1 year (approximately). If the modem is powered
down, the M&C microcontroller carry out the following sequence.

1. When power is applied to the M&C, the microcontroller checks the non-volatile

memory to see if valid data has been retained. If valid data has been retained, the
modem is reconfigured to the parameters maintained by the RAM.

2. If the non-volatile memory fails the valid data test, a default configuration from

ROM is loaded into the system.

The UART supports serial ASYNC communications channels (remote port) with a
maximum data rate of 19200 bit/s. The UART is a built-in peripheral of the
microcontroller. The communications type can be EIA-232, EIA-485 (2-wire),
and software selectable.

The ASK UART operates at a data rate of 9600 bit/s. The modulator modulates at
312.5 kHz carrier with the data to be transmitted to the ODU. This carrier is multiplexed
onto the modulator cable. The ASK demodulator converts the 312.5 kHz signal received
on the modulator cable from the ODU into a data stream for the UART. The
communications sequence is initiated by the IDU and the ODU sends a response within a
specified time limit.

The DAC supplies a voltage that controls the contrast of the display. The ADC monitors
all the voltages from the power supply. The DAC and ADC are mapped to the
Microcontroller with an Integrated Circuit (IC) bus.

The user interface includes the following parts:

! Front panel
! Status LEDs
! Keyboard
! Sounder (beeper)

All functions are memory-mapped to the microcontroller.

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