Comtech EF Data C5 - Manual (Page 250)

Options C5/K1/K3 Integrated Satellite Terminal System
A–6 Rev. 0
A.2 Interface Options
A.2.1 Asynchronous Interface/AUPC
The asynchronous (ASYNC) interface option provides the interface for terrestrial data
and a single ASYNC overhead channel. Typically used for earth-station-to-earth-station
communication, the overhead channel is multiplexed onto the data and transmitted at an
overhead rate of 16/15 of the main channel. The AUPC feature works with the ASYNC
option to allow remote communication between a local modem and a remote modem.
Refer to Figure A-1 for a modem block diagram with the ASYNC/AUPC interface
option.
EIA-422, or V.35 interfaces are available for terrestrial data input and output. These
interfaces can be selected via the front panel.
EIA-485 or EIA-232 interfaces are available for ASYNC channel input and output. These
interfaces can also be selected from the front panel. Fixed 1/15 overhead is added to the
data when an ASYNC channel is being used. With the ASYNC channel enabled, the
terrestrial data rate can be from 8 to 2048 kbit/s. The ASYNC channel I/O protocol can
be as follows:
Baud 110 to 38400
Data Bits 5 to 8
Parity odd, even, or none
Stop Bits 1 or 2
Note: Certain combinations of baud rate, data rate, parity, and stop bits will limit the
maximum baud rate allowed for continuous throughput based on terrestrial data rate.
ASYNC overhead is a 1/15 rate overhead channel composed of the following:
! AUPC information (if installed)
! EIA-232 or EIA-485 data
! Framing information
! Parity bits
! Valid data flags
The rate of asynchronous data transfers may be selected by the operator, with the
maximum rate available limited to 1.875
% of the synchronous data rate.