Q-Flex Satellite Modem Installation and Operating Handbook
9-5
Min
Req
Signal Description
RS422
Name
Circuit
Number
25 pin
Electrical
Levels
A
B
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In
TT
113
24
11
RS422
Data In
SD
103
2
14
RS422
Sig
’
Valid In
RS
105
4
19
RS422
Sig Accpt
’
d Out
CS
106
5
13
RS422
Int
’
Tx Clock Out
ST
114
15
12
RS422
DATA CIRCUIT FROM MODEM (RX)
Clock Out
RT
115
17
9
RS422
Data Out
RD
104
3
16
RS422
Sig
’
Valid Out
RR
109
8
10
RS422
COMMON LINES
Signal Ground
SG
102
7
Ground
Shield/Protective ground
PG
101
1
Screen
Device (DTE) Ready In
TR
108
20
23
RS422
Device (DCE) Ready Out
DM
107
6
22
RS422
Local Loop In
LL
141
18
RS232
Remote Loop In
RL
140
21
RS232
Th
e maximum data rate is 10Mbps (over good quality twisted pair screened cable), but this
rate is reduced as the connecting cables extend beyond 10m. As an estimate, assume the
maximum rate halves as the distance doubles (ie 5Mbps to 20m, 2.5Mbps to 40m etc).
The input clock/data phase is selected automatically, reporting a `Data Marginal` warning
whenever it has to switch phase. If the modem reports Data Marginal frequently then this is
not a modem fault but an indication that you have a clocking problem external to the
modem (i.e. changing clock/data phase, a problem which would otherwise cause
untraceable data errors). With the Tx Clocking Set to
Tx Clock In
the `Data In` signal is
checked against the `Clock In` signal. With the Tx Clocking Set to
Internal
or
Rx
the `Data
In` signal is checked against the `Int= Tx Clk Out` signal.
By selecting
Advanced
it is possible to configure the modem to raise an alarm if either the
`Sig= Valid In` line (RS) or `Device (DTE) Ready In` line (TR) switch to the inactive state. It
is also possible to configure the Tx carrier to be switched on and off by the `Sig= Valid In`
line (RS) by selecting
Change
,
Tx
,
Modulator
,
Carrier
,
RTS-Controlled
.