P1440 In X.21 Mode - Paradise Datacom P300 Series Installation & Operating Handbook

P1440 IN X.21 MODE

The P300 Series along with its standard P1440 RS422/V.35/RS232 interface can provide both X.21
DCE and X.21 DTE operation. For X.21 operation the card must be set to RS422 mode, and the Tx & Rx
Clocking modes must be set correctly. With the use of the appropriate adaptor lead (to convert to the
X.21 standard 15 pin D connector), a full X.21 DCE or DTE interface is available.
X.21 DCE OPERATION
This only has a clock from the modem to the terrestrial equipment. Configure a cable with a 15 pin `D`
female at one end (X.21 DCE) and either a 25 pin or 37 pin `D` male (not both) at the other end as
follows:
Min X.21 DCE
Req
(15 pin D female)
Name A
DATA CIRCUIT TOWARDS MODEM (TX)
T 2
C 3
DATA CIRCUIT FROM MODEM (RX)
S 6
R 4
I 5
COMMON LINES
Sig gnd 8
Prot gnd 1
Clocking: IMPORTANT
The interface will not work as X.21 unless you set the clocking correctly! The Rx Clock Menu is used to
set the source of the single clock from the modem as
as this does not exist in X.21. The Tx Clocking should simply be set to
clocked by the same clock as the Rx data.
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). Check the phase of the Data In
with respect to the Clock Out line.
By selecting ,
either the `Sig` Valid In` line (C) switches to the inactive state. As there is no X.21 equivalent of the
RS422 `Device (DTE) Ready In` line (TR), set this to
carrier to be switched on and off by the `Sig` Valid In` line (C) by selecting
, .
P300H P300 Series Modem Installation and Operating Handbook
Signal RS422
Description Name
B
9 SD
Data In
`
Sig Valid In
10 RS
13 Clock Out RT
11 Data Out RD
`
Sig Valid Out
12 RR
SG
Signal Ground
`
Shield / prot PG
ground
, it is possible to configure the modem to raise an alarm if
Circuit 25 pin
Number
A B A
103 2 14 4
105 4 19 7
115 17 9 8
104 3 16 6
109 8 10 13
102 7 19, 20, 21
101 1
, , or
. It is also possible to configure the Tx
37 pin Electrical
Levels
B
22 RS422
25 RS422
26 RS422
24 RS422
31 RS422
Ground
1 Screen
. Do not select
as the Tx data is
, , ,
Page 176