Comtech EF Data SDM-2020, Installation And Operation Manual

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Data Interfaces SDM-2020 Satellite Demodulator
A–34 Rev.3
A.5.4.3 Terrestrial Extended Signal Definitions
The HSSI specification has no provision for SYNC or DVALID signals. If terrestrial data
framing is desired, a sync byte (47 hex) is embedded into the data stream every 188 or
204 bytes, as selected in the modulator configuration. The modulator detects the sync
byte and formats the serial interface into a standard, error-protected 204 byte packet.
In order to support TM1449, PSYNC and DVALID will be routed to RESERVED (from
DCE) HSSI pins. Refer to Table A-17 for definition of signals.
Table A-17. Definition of Signals
Signal Definition
Transmitter Synchronization Signal (TX PSYNC) Indicates the beginning of a transport packet by signaling the SYNC
byte. Active per defined format timing.
Transmitter Data Valid (TX DVALID) Indicates valid data at the interface. Active per defined format timing.
Carrier Detect (CD) Indicates Demodulator carrier tracking loop locked. Status output. TTL
output. Active High (programmable).
Demodulator Fault (DF) Open collector TTL signal indicating Demodulator Fault. Active High.
External pull-up required.
Modulator Fault (MF) Open collector TTL signal indicating Modulator Fault. Active High.
External pull-up required.
Receiver Synchronization (RX PSYNC) Indicates the beginning of a transport packet by signaling the SYNC
byte. Active per defined format timing.
Receiver Data Valid (RX DVALID) Indicates valid data at the interface. Active per defined format timing.