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CDM-625 Advanced Satellite Modem
EDMAC Channel
of 19,200 baud. It should be pointed out that at 2.4 kbps, the effective throughput of the overhead
channel is only 11 async characters/second. For a message of 24 bytes, the time between sending
a poll request and receiving a response will be around 5 seconds. (Note that when either of the
BPSK Turbo rates is in use, the overhead rate is reduced by a factor of three, and therefore the
response time will be around 15 seconds.)
11.3 Setup Summary
To access a distant-end unit:
Designate a Master/Slave pair: Master at the local-end, Slave at the distant-end.
On the local-end unit, enable framing and EDMAC, define the unit as MASTER, then
enter the bus address. This is constrained to be 'base 10' meaning that only addresses
such as 10, 20, 30, 40 etc, are allowed.
Choose a unique bus address for the distant-end. This should normally be set to the 'base
10' address + 1. For example, if the MASTER unit is set to 30, choose 31 for the distant-
end unit.
On the distant-end unit, enable framing and EDMAC, define the unit as SLAVE, then
enter the bus address. The orange EDMAC Mode LED on the modem front panel should
be illuminated.
Set the local-end unit to RS485 remote control, and set the bus address of this local unit.
The orange Remote Mode LED on the modem front panel should be illuminated.
Once the satellite link has been established, connect the M&C Computer, and begin
communications with both the local and distant end units.
NOTE: EDMAC modes are fully compatible with AUPC modes.
11.4 Drop & Insert ++
A new variation of EDMAC is available with D&I++ framing. With this, each frame contains
2944 bits, with 64 overhead bits and 2880 user data bits. The portion of the overhead used for the
EDMAC link performs identically to that of the EDMAC frame, but because D&I++ uses a
smaller overhead, the two modes are not compatible with each other.
MN-0000036 (Ref MN/CDM625.IOM)
11–3
Revision 1
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