Comtech EF Data SMS-458B - Manual (Page 77)

SMS-458B Modem Protection Switch Revision 2
Theory of Operation MN/SMS458B.IOM
4–17
3
EXT CONTROL BUS
DATA BUS AND
CONTROL SIGNALS
ADDRESS
LATCH
ADDRESS
DECODE AND
DATA BUS
BUFFER
INTERNAL
CONTROL BUS M:N
FAULT
3
3
DMD SYSTEM
FAULT
FAULT
CONTROL
RELAY-REMOTE
INTERFACE
4
MUX
'1'
RS-485
RS-232
DSR
RXD
TXD
EXT INTERFACE CONTROL
20
PRIME AND
FAULT INPUTS
BACKUP
MODEM INTERFACE CONTROL
COMMUNICATIONS
ASYNCHRONOUS
INTERFACE
DEVICE
ASYNCHRONOUS
COMMUNICATIONS
INTERFACE
DEVICE
RS-485
Figure 4-5. Address Decoder/Driver
4.3.2 Specifications
Address Decoding 2K bytes of address bus decoded to 24 discrete channels.
Data Bus Buffering 8 bits to all peripheral devices.
Communication Interface:
Remote interface
Relay-remote interface
Modem Control Interface
EIA-485 or EIA-232, 255 addresses, 110 to 9600 baud.
4 lines (parallel).
EIA-485, 255 addresses, 9600 baud.
(Dual ACIAs on the AS/1048 board enable simultaneous
communication on both Remote and Modem control
interfaces.)
Modem Fault Interface 10 lines for Muxed modulator and demodulator faults.
Fault Outputs Controller Fault: Form-C.
System Fault: Form-C.
Demod Signal Fault: Form-C.