DMD2401 LB/ST L-Band Satellite Modem and ODU Driver
Operation
TM075 - Rev. 1.3
3-11
3.10.4.1 Insert Terrestrial Frame Source
The insert terrestrial frame source selection tells the modem where the insert terrestrial frame is
coming from. External means the terrestrial frame is to be input via the Insert Data In port.
Internal means that the modem needs to generate the terrestrial frame and that all non-inserted
timeslots need to be filled with the appropriate idle code based upon the terrestrial framing (T1 or
E1). In addition, the selection of the insert terrestrial frame source also influences the Buffer
Clock selection in the following manner:
When the insert terrestrial frame source selection is set to External, the received satellite data
will be clocked out of the Doppler buffer based upon the clock recovered from the insert data
input. Therefore, the Buffer Clock selection will automatically be set to External and cannot be
modified.
When the insert terrestrial frame source selection is set to Internal, the operator needs to specify
how data should be clocked out of the Doppler buffer. In this case, the operator will be able to
select either SCTE, SCT, or RX SAT as the source for the Buffer Clock. Therefore, the insert
terrestrial frame source selection should be made prior to attempting to change the Buffer Clock.
In most instances, the insert terrestrial frame source selection will be set to External and the
Buffer Clock will automatically be set to External.
3.10.5 Alarms
The following alarms are unique to Drop & Insert and vary based on the terrestrial framing:
Alarms
Modem Alarms
Active Alarms
Minor Tx
Drop Alarms
FrmLock – Indicates Terrestrial Frame lock on the Send Data Port.
Valid in all framing modes
MFrmLck – Indicates Terrestrial Multiframe lock on the Send Data Port.
Valid in PCM-30, PCM-30C
CRCLock – Indicates valid CRC received via the Send Data Port.
Valid in PCM-31C, PCM-30C
SigData – Indicates valid signaling data received via the Send Data Port.
Valid in PCM-30, PCM-30C
Minor Rx
Insert Alarms
FrmLock – Indicates Terrestrial Frame lock on the Receive Data Port.
Valid in all framing modes
MFrmLck – Indicates Terrestrial Multiframe lock on the Receive Data Port.
Valid in PCM-30, PCM-30C
There are also additional Backward Alarms available in Drop & Insert Mode
Alarms
Modem Alarms
Backward Alarms
Prompt – This is the prompt maintenance alarm output by the modem
Service – This is the deferred service alarm output by the modem
TerBack – Indicates whether or not a terrestrial backward alarm is being received
SatBack – Indicates whether or not a satellite backward alarm is being received
which would be caused by the demod losing lock at the other end of the
link
