FEC Onlineservices
 
X.21-'Back-to-Back'-connection for X.21-interfaces with automatic cable detection
Besides the basic references regarding the 'Back-to-Back'-connection of two X.21 interfaces with automatic cable detection, the required PIN assignment for the cable is specified.

Preliminary Note:
For testing purposes it is helpful to link two Bintec routers via the X.21 interface directly (Back-to-Back). The X.21 interface is available in two different types:
  • X.21-interface without automatic cable detection: 

    Concerns: Router X4000, ModuleCM-X21
    Type: 26-pin Mini-Delta-Ribbon-connector at  X4000, DB-15 connector at CM-X21 
    Same cable for DTE- and DCE-operation
    Automatic cable detection: No

  • X.21-interface with automatic cable detection:

    Concerns: Router X2100, X4300, Module 8E-SYNC
    Type: 26-pin Mini-Delta-Ribbon-connector
    Different cable for DTE- and DCE-operation
    Automatic cable detection: Yes

Connecting two X.21 interfaces with automatic cable detection
First a DTE- has to be connected to a DCE cable:

- BinTec X.21 DTE cable (Mini Delta Ribbon 26-pin to D-Sub15/male, Art.Nr. 14076)
- BinTec X.21 DCE cable (Mini Delta Ribbon 26-pin to D-Sub15/female, Art.Nr. 14077)

After connection to the X.21 interfaces, the interface types and connector types are detected automatically and displayed in the Setup Tool.

Example: X8500 with X8E-SYNC as DCE, X2100 as DTE

x8500:> debug all&
14:26:09 DEBUG/X.21: SI3-0: nxser_L1SetState(): DCE-L1-state: up 2048000 bit/s
14:26:09 DEBUG/PPP: si3-0: leased line connection established
x8500:>

 

X8500 Setup Tool                                       BinTec Communications AG
[SLOT 3 UNIT 0 SERIAL]: Configure Serial Interface - Unit 0               x8500
_______________________________________________________________________________

          Cable Detection          interface & connector type

          Interface Type           X.21 (term)  (autodetected)
          Connector                dce          (autodetected)

          Speed                    2 Mbit/s

          Layer 2 Mode             auto

          Interface Leads          enabled

                    SAVE                               CANCEL
_______________________________________________________________________________


x2100:> debug all&
14:38:05 DEBUG/X.21: si300: DTE-L1-state: up  2038000 bit/s
14:38:05 DEBUG/PPP: si3-0: leased line connection established
x2100:>

X2100 Setup Tool                                       BinTec Communications AG
[SLOT 3 SERIAL]: Configure Serial Interface - Unit 0                      x2100
_______________________________________________________________________________

          Cable Detection          interface & connector type

          Interface Type           X.21 (term)  (autodetected)
          Connector                dte          (autodetected)

          Layer 2 Mode             auto

          Interface Leads          enabled

                    SAVE                               CANCEL
_______________________________________________________________________________
The configuration of the X.21-WAN-Parter is done as usual.

Pin assignment of a special 'Back-to-Back'-cable
For a special 'Back-to-Back'-cable the pins should be connected as follows:

X.21/DTE X.21/DCE Description
Signal Pin Pin Signal
Screen 1 1 Screen Protective earth
GND 2 2 GND Signal earth
TxD(B) 3 5 RxD(B) Data
TxD(A) 4 6 RxD(A)
RxD(B) 5 3 TxD(B)
RxD(A) 6 4 TxD(A)
RTS(B) 7 9 CTS(B) Control/Indication
RTS(A) 8 10 CTS(A)
CTS(B) 9 7 RTS(B)
CTS(A) 10 8 RTS(A)
RxC(B) 11 25 TxCE(B) Clock
RxC(A) 12 26 TxCE(A)



Additional pins for automatic detection of the X.21-connector (X.21/DTE and X.21/DCE):

Description Pin X.21/DTE X.21/DCE
Mode DCE 13 N/C GND
Mode 0 14 N/C N/C
Mode 1 23 N/C N/C
Mode 2 24 GND GND


N/C = not connected

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