Comtech EF Data SMS-458B - Manual (Page 64)

SMS-458B Modem Protection Switch Revision 2
Theory of Operation MN/SMS458B.IOM
4–4
To turn ON any switch, move it to the position closer to the PCB. See the following
examples.
Address SP2-1 SP2-2 SP2-3 SP2-4 SP2-5 SP2-6 SP2-7 SP2-8
1 OFF OFF OFF OFF OFF OFF OFF ON
3 OFF OFF OFF OFF OFF OFF ON ON
5 OFF OFF OFF OFF OFF ON OFF ON
9 OFF OFF OFF OFF ON OFF OFF ON
17 OFF OFF OFF ON OFF OFF OFF ON
33 OFF OFF ON OFF OFF OFF OFF ON
65 OFF ON OFF OFF OFF OFF OFF ON
129 ON OFF OFF OFF OFF OFF OFF ON
255 ON ON ON ON ON ON ON ON
4.1.2.4 External Remote Serial Interface Selection
An EIA-485 or EIA-232 communications link on the address decoder/driver module
provides remote serial interface for all switch functions.
The
EIA- 485 interface allows up to 32 devices to operate on a common communication
link. Each device must have a discrete address (there are 255 discrete addresses). EIA-
232 communication is only possible with a single device. During configuration setup, the
switch is configured for EIA-232 communication, whether EIA-232 or EIA-485
communication is desired. See Figure 4-1 for location of the switches.
Use M&C module switch pack SP1 switch 5 (SP1-5) to configure each switch for
external remote interface type, either EIA-485 or EIA-232. The ON position (nearer the
PCB) selects EIA-232 interface and OFF selects EIA-485.
4.1.2.5 Battery
A rechargeable battery on the M&C module allows it to retain configuration and status
information for up to 30 days without prime power. M&C module jumper JP6 connects
battery power to the backup RAM. During normal operation, this jumper should be in the
ON position.
Should the switch be powered-down, the M&C microcontroller performs the following
sequence:
1. Upon power-up, the M&C microcontroller checks the battery-backed RAM for
valid data. If valid data has been retained, the M&C implements the RAM-stored
switch configuration.
2. If the battery-backed RAM fails the valid data test, the switch loads default
settings from ROM.