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Data Interfaces
A.5.5
Monitor and Control Functions
A.5.5.1
System Implementation
Refer to Table A-21 for signal definition.
Signal
TA (Data Terminal Equipment Available)
LA (Loopback Circuit A)
LB (Loopback Circuit A)
CA (Data Communication Equipment Available)
LC (Loopback Circuit C)
TM (Test Mode)
TA
LA and LB loopback input control signals
Upon Modem power-up the CA output is set UNAVAILABLE until all modem
initialization has been completed and no faults are detected. After completion of
initialization the CA line is set AVAILABLE. Any detectable faults that cause the
modem to be place in an non-operational mode shall set CA UNAVAILABLE.
TM output shall be set ACTIVE if the ECL/HSSI interface is commanded into Loopback
mode. TM shall be INACTIVE for all other modes.
LC output is not supported, and is set inactive for all modes.
A.5.5.2
Faults
Refer to Table A-22 for ECL/HSSI fault indicators to the HSSI connector (Reserved
DCE pins) from the modem interface.
Signal
Carrier Detect (CD)
Modulator Fault (DF)
Modulator Fault (MF)
A–38
Table A-21. Signal Definition
These signals are inputs from the HSSI interface. The state of these inputs is
read by the M&C from the ECL/HSSI interface status register.
These signals are outputs from the HSSI interface. The state of these outputs
is controlled by the M&C writing the ECL/HSSI interface control register.
This signal indicates the DTE is available for data transfers. When the DTE
is not available the RF output will be turned Off and the DTE status menu
shall reflect DTE unavailable.
These signals are available to the M&C, but no functional support is
required.
Table A-22. Fault Signal Definitions
Indicates Demodulator carrier tracking loop locked. Status output. TTL output. Active
High (programmable).
Open collector TTL signal indicating Demodulator fault. Active High. An external
pull-up resistor is required.
Open collector TTL signal indicating Modulator fault. Active High. An external pull-
up resistor is required.
SDM-2020 Satellite Demodulator
Definition
Definition
Rev.3
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