Comtech EF Data SDM-9000 - Manual (Page 131)

SDM-9000 Satellite Modem Theory of Operation
Rev.4 5–3
The heart of the M&C card is the Intel 80C32 (or a compatible microcontroller)
operating at 16 MHz. This microcontroller contains 256 kbytes of internal RAM. At
U17, a ROM can be:
•
27C010 (128 kbytes)
•
27C020 (256 kbytes)
•
27C040 (512 kbytes)
ROM access times must be
≥
200 ns. The correct ROM size can be set by jumpers JP9
and JP10. The RAM can be 8 or 32 kbytes in size. This RAM chip is internally battery-
backed and contains a real time clock used by the M&C.
The nonvolatile RAM on the M&C module will retain configuration information without
prime power for up to one year. 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 nonvolatile
memory to see if valid data has been retained. If valid data has been retained, the
modem is reconfigured to those parameters.
2. If the nonvolatile 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 memory mapped to the microcontroller.
The communications type can be RS-232 or RS-485 (set with M&C jumpers JP1 and
JP5). For RS-485 communications, 2- or 4-wire operation can be set by jumpers JP2 and
JP3. The remote port is connected to the M&C system interface connector (JP4).
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 I
2 C bus.
The inter-modem communications use the internal serial port located in the
microcontroller. The inter-modem communications are connected to the M&C system
interface connector (JP4) for communication between the modulator, demodulator, and
interface cards.
The user interface includes the following parts:
•
Front panel
•
Status LEDs
•
Keyboard
•
Sounder (beeper)
All functions are memory mapped to the microcontroller.