Comtech EF Data DMD-2050E - Manual (Page 61)

DMD2050E Universal Satellite Modem Theory of Operation
MN-DMD2050E Revision 2 3–19
3.6.4 Ethernet Data Interface (Optional)
The modem support a single port 10/100/1000 Base T Interface. When this interface is selected
additional menus will be displayed. Refer to Appendix H for interface set up and description of
supporting features.
When Ethernet Data Interface is selected, the Tx Clock Source will default to SCTE and the Clock
Polarity will default to Normal. In addition, the Buffer Clock will default to RxSat and the Buffer
Clock Polarity will default to Normal.
3.7 Receive Timing Options
Any of the clocking selections, SCTE, SCT, EXT CLK, or RxSat (SCR) may be selected as the
Buffer Clock. Data will be clocked out of the buffer at the data rate synchronous to the selected
clock source.
3.7.1 Loop Timing
If loop timing is desired (i.e.; the modem timing is slaved to the far end master station), the
modem clocks can be configured as follows:
3.7.2 Transmit (MIL-188-114A, RS-422)
Set SCT Source to ‘SCR’. The Tx Terminal Equipment must clock the TX Data with the SCT
Clock and return data and SCTE (Optional). If SCTE is returned to the modem from the terminal
equipment, set TX CLK SRC to SCTE. If SCTE is not returned to the modem, set TX CLK SRC
to SCT. The TX CLK POL should be set to AUTO.
3.7.3 G.703 Interface or Asymmetrical Data Rates
Loop timing with a G.703 Interface or Asymmetrical Data Rates requires external equipment at
the remote end that is capable of using the recovered RD Clock as source timing for (SCTE) SD.
The modem will not manipulate the clock frequency. Therefore, the transmit and receive clock
rates must be equal in order for the modem to perform loop timing.
3.7.4 Receive
Select the Buffer clock to RxSAT (SCR).