Comtech EF Data SNM-1000 - Manual (Page 119)

4–1
Chapter 4. THEORY OF OPERATION
This chapter describes the theory of operation for the following printed circuit boards
(PCBs) contained in the SNM-1000.
• DAC
• Monitor & Control (M&C) Board
• Modulator
• Demodulator
4.1 Demand Assignment Controller (DAC)
The DAC performs DAMA control inbound/outbound functions within the SNM-1000.
The DAC is capable of remotely controlling in-circuit reconfiguration of the DAMA
microcontroller code. The DAC performs the following functions:
• Decodes a network control HDLC encoded data stream from the demodulator
• Encodes a burst signal using HDLC encoding
• Synchronizes transmit burst to control slot time
• Controls the data interface
• Controls the modem M&C board via a serial link
• Supports two EIA-232 user interface ports
• Supports two EIA-485 interface ports
The SNM-1000 interfaces with the DAC through an interface bus connector. Eleven
external and internal interfaces are provided as permanent installations on the DAC
board.
A block diagram of the DAC is shown in Figure 4-1.