Theory Of Operation; Figure 4-8. Rs-232-C Interface - Comtech EF Data SDM-100A Installation And Operation Manual

SDM-100A Satellite Modem
P5
5 TT
6 SD
7 RS
13 MC
15 DF
16 MF
10 RT
8 ST
9 DM
14 CS
11 RD
12 RR
30 -CP
33,34 +12V
35,36 -12V
37,38 +5V
4 INF1
1,2 GND
39,40 GND
3 INF0

4.4.3.1 Theory of Operation

The RS-232-C interface provides a Send Timing (ST) clock signal at the modem data
rate. This signal may be set to NORMAL or INVERT at jumper P3 on the Interface
board.
•
•
In either case, the phase relationship between the clock and data is not important as long
as it meets the jitter specifications of RS-422/449. This is because a clock phase
correction circuit is provided, which shifts the clock away from the data transition times.
Rev. 0
TT DA
SD
DF DF
MF MF
RT

Figure 4-8. RS-232-C Interface

In the INTERNAL clock mode, the data to be transmitted, Send Data (SD), must
be synchronized to ST.
In the EXTERNAL clock mode, the clock is accepted on the Terminal Timing
(TT) input to clock-in the data to be transmitted.
BA
RS CA
MC -MC
DD
ST DB
DM CC
CS CB
RD BB
RR CF
CP
-
Theory of Operation
J1
DA (TT) 24
BA (SD) 2
CA (RS) 4
-MC 9
DEMOD FAULT
11
MOD FAULT 25
DD (RT) 17
DB (ST) 15
CC (DM) 6
CB (CS) 5
BB (RD) 3
CF (RR) 8
CP 18
GND 1,7
CP
4–23