SLM-3650 Satellite Modem
Revision 3
Theory of Operation
MN/SLM3650.IOM
4–3
The heart of the M&C card is the Dallas 80C310 microcontroller operating at 11 MHz.
This microcontroller contains 256 kbytes of internal RAM. The ROM at U8 is 29F040
(512 kbytes).
ROM access times must be equal to or greater than 150 ns. The RAM can be 8 kbytes or
32 kbytes in size. This RAM chip is internally battery-backed and contains a real time
clock used by the M&C.
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 following sequence is carried out by the M&C microcontroller.
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 bps. The UART is a built-in peripheral of the
microcontroller. The communications type can be EIA-232, EIA-485 (2-wire),
EIA-485 (4-wire), software selectable.
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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