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P300H P300 Series Modem Installation and Operating Handbook Page 168
P1440 IN RS422 MODE
The P1440 is the standard interface supplied with the P300 Series Modem. If RS422 is selected under
Change, Terr-Intfc, Electrical then the following interface description applies.
Min RS422 Circuit Electrical
Req Name Number Levels
Signal Description
25 pin 37 pin
ABAB
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In TT 113 24 11 17 35 RS422
Data In SD 103 2 14 4 22 RS422
Sig’ Valid In RS 105 4 19 7 25 RS422
Sig Accpt’d Out CS 106 5 13 9 27 RS422
Int’ Tx Clock Out ST 114 15 12 5 23 RS422
DATA CIRCUIT FROM MODEM (RX)
Clock Out RT 115 17 9 8 26 RS422
Data Out RD 104 3 16 6 24 RS422
Sig’ Valid Out RR 109 8 10 13 31 RS422
COMMON LINES
Signal Ground SG 102 7 19, 20, 21 Ground
Shield/Protective ground PG 101 1 1 Screen
Device (DTE) Ready In TR 108 20 23 12 30 RS422
Device (DCE) Ready Out DM 107 6 22 11 29 RS422
Local Loop In LL 141 18 10 RS232
Remote Loop In RL 140 21 14 RS232
The 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 (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.
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 (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.