P300H
P300 Modem Installation and Operating Handbook
Page 159
P1440 IN RS232 MODE
The P1440 is the standard interface supplied with the P300 Modem. If RS232 is selected under
Change
,
Terr-Intfc
,
Electrical
then the following interface description applies.
Min
RS232
Circuit
Electrical
Req
Name
Number
Levels
Signal Description
25 pin
37 pin
A
B
A
B
DATA CIRCUIT TOWARDS MODEM (TX)
8
Clock In
DA
113
24
17
RS232
8
Data In
BA
103
2
4
RS232
Sig’ Valid In
CA
105
4
7
RS232
Sig Accpt’d Out
CB
106
5
9
RS232
Int’ Tx Clock Out
DB
114
15
5
RS232
DATA CIRCUIT FROM MODEM (RX)
8
Clock Out
DD
115
17
8
RS232
8
Data Out
BB
104
3
6
RS232
Sig’ Valid Out
CF
109
8
13
RS232
COMMON LINES
8
Signal Ground
AB
102
7
19, 20, 21
Ground
8
Shield/Protective ground
SHIELD
101
1
1
Screen
Device (DTE) Ready In
CD
108
20
12
RS232
Device (DCE) Ready Out
CC
107
6
11
RS232
Local Loop In
LL
141
18
10
RS232
Remote Loop In
RL
140
21
14
RS232
The maximum data rate is 100kbps (over good quality 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 50kbps to 20m, 25kbps to 40m etc). NOTE this is a synchronous RS232 interface, if you need
an asynchronous interface, please contact the factory.
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 (ie changing clock/data phase, a
problem which would otherwise have caused 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.
Note that although there are both 25 pin EIA530 pinout and 37 pin RS449 pinout connectors on the rear
panel, these are simply connected in parallel. Do not use both connectors at the same time. The EIA530
connector is pin compatible with the standard 25 pin RS232 interface.
By selecting
Change
,
Terr-Intfc
,
Control Lines
it is possible to configure the modem to raise an alarm if
either the `Sig’ Valid In` line (CA) or `Device (DTE) Ready In` line (CD) 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 (CA) by selecting
Change
,
Tx
,
Modulator
,
Carrier
,
RTS-Controlled
.
