Comtech EF Data CDM-500 - Manual (Page 60)

CDM-500 Closed Network Satellite Modem EDMAC Channel
Rev. 1.3 8–3
This approach does not require any additional cabling - connection is made using the
normal M&C remote port. Furthermore, the user does not have to worry about
configuring the baud rate of the M&C connection to match the lowest data rate modem in
the system. The M&C system can have mixed data-rate modems, from 2.4 kbps to 512
kbps, and still run at 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.)
8.3 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 of the SLAVE. 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 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 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.