Westermo MR Series - Manual (Page 431)

431 6622-3201
Web Interface and Command Line Reference Guide www.westermo.com
X.21 25-Pin to 15-Pin Straight Through Cable – External Clock 21.1.3
This is normally the cable to use to connect an X.21 terminal (e.g. an ATM) to the Westermo. Use
this cable when the Westermo is the clock sink or configured as “external clock”.
25-way D - Westermo Side 15-way D
13
25 14
1 1
9 15
8
Signal Pin # (DCE) Pin # (DTE) Signal
Frame Ground (Case) Shield Shield Frame Ground (Case)
TxDA 2 2 TxDA
RxDA 3 4 RxDA
CTLA 4 3 CTLA
INDA 5 5 INDA
GND 7 8 GND
CLKB 11 13 CLKB
INDB 13 12 INDB
TxDB 14 9 TxDB
RxDB 16 11 RxDB
CTLB 19 10 CTLB
CLKA 24 6 CLKA
N.B. Frame Ground is optional.
Note:
When operating an X.21 (RS-422) link Synchronously it is necessary to fit termination resistors
to each signal pair at the receiving end. The Westermo already has in-built terminating resistors,
but terminating resistors will need to be fitted between the TxDA & TxDB pins, CLKA & CLKB
pins and CTLA & CTLB pins at the DTE.