Terrestrial Extended Signal Definitions; Table A-17. Definition Of Signals - Comtech EF Data SDM-2020 Installation And Operation Manual

Data Interfaces
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.
Signal
Transmitter Synchronization Signal (TX PSYNC)
Transmitter Data Valid (TX DVALID)
Carrier Detect (CD)
Demodulator Fault (DF)
Modulator Fault (MF)
Receiver Synchronization (RX PSYNC)
Receiver Data Valid (RX DVALID)
A–34

Table A-17. Definition of Signals

Indicates the beginning of a transport packet by signaling the SYNC
byte. Active per defined format timing.
Indicates valid data at the interface. Active per defined format timing.
Indicates Demodulator carrier tracking loop locked. Status output. TTL
output. Active High (programmable).
Open collector TTL signal indicating Demodulator Fault. Active High.
External pull-up required.
Open collector TTL signal indicating Modulator Fault. Active High.
External pull-up required.
Indicates the beginning of a transport packet by signaling the SYNC
byte. Active per defined format timing.
Indicates valid data at the interface. Active per defined format timing.
SDM-2020 Satellite Demodulator
Definition
Rev.3