EIA/TIA-232 DTE Cable Pinout (DB60 to DB25)
The Cisco EIA/TIA-232 DTE cable connects the proprietary 60-pin DB-60 connector on Cisco 4000, 4500, and 4700 series routers to a standard DB-25 connector at the network end, implementing the ANSI/TIA-232-F (RS-232) single-ended signalling standard. EIA/TIA-232 uses unbalanced signalling at ±3 V to ±12 V, with a nominal maximum data rate of 20 kbit/s over cable lengths up to 15 m, though it is commonly used at higher rates over short distances. The DTE cable carries a male plug at the network (DB-25) end; the complementary DCE variant (CAB-232FC) carries a female receptacle. Interface type and DTE/DCE mode are selected by the shorting group on MODE_0, GND, and MODE_DCE pins of the DB-60 connector.
| 60 Pin1 | Signal | Description | Direction | 25 Pin | Signal |
|---|---|---|---|---|---|
| J1-50 J1-51 J1-52 | MODE_0 GND MODE_DCE | Shorting group | - | - | - |
| J1-46 | Shield GND | Single | - | J2-1 | Shield GND |
| J1-41 Shield | TxD/RxD - | Twisted pair no. 5 | → - | J2-2 Shield | TxD - |
| J1-36 Shield | RxD/TxD - | Twisted pair no. 9 | ← - | J2-3 Shield | RxD - |
| J1-42 Shield | RTS/CTS - | Twisted pair no. 4 | → - | J2-4 Shield | RTS - |
| J1-35 Shield | CTS/RTS - | Twisted pair no. 10 | ← - | J2-5 Shield | CTS - |
| J1-34 Shield | DSR/DTR - | Twisted pair no. 11 | ← - | J2-6 Shield | DSR - |
| J1-45 Shield | Circuit GND - | Twisted pair no. 1 | - - | J2-7 Shield | Circuit GND - |
| J1-33 Shield | DCD/LL - | Twisted pair no. 12 | ← - | J2-8 Shield | DCD - |
| J1-37 Shield | TxC/NIL - | Twisted pair no. 8 | ← - | J2-15 Shield | TxC - |
| J1-38 Shield | RxC/TxCE - | Twisted pair no. 7 | ← - | J2-17 Shield | RxC - |
| J1-44 Shield | LL/DCD - | Twisted pair no. 2 | → - | J2-18 Shield | LTST - |
| J1-43 Shield | DTR/DSR - | Twisted pair no. 3 | → - | J2-20 Shield | DTR - |
| J1-39 Shield | TxCE/TxC - | Twisted pair no. 6 | → - | J2-24 Shield | TxCE - |
Notes
- Arrows indicate signal direction: → indicates DTE to DCE, and ← indicates DCE to DTE.
- (1) Any pin not referenced is not connected.
- The DB-60 connector is used on the router end of all classic Cisco WAN serial cables for the 4000-M, 4500-M, and 4700 series; the interface type is determined solely by which cable is attached.
- The shorting group at J1-50 (MODE_0), J1-51 (GND), and J1-52 (MODE_DCE) selects the signalling standard and DTE/DCE mode on the DB-60 port.
- EIA/TIA-232 uses unbalanced (single-ended) electrical signalling; signals are paired with a shield in the cable to reduce noise, but they do not form true differential pairs.
- The DTE cable part number is CAB-232MT; the DCE counterpart is CAB-232FC. On Cisco cables, the suffix MT indicates a male (DTE) connector at the network end, and FC indicates a female (DCE) connector.
Signals
- TxD — Transmitted Data; serial data sent from the DTE (router) to the DCE.
- RxD — Received Data; serial data received by the DTE from the DCE.
- RTS — Request to Send; asserted by the DTE to indicate readiness to transmit.
- CTS — Clear to Send; asserted by the DCE to grant the DTE permission to transmit.
- DSR — Data Set Ready; asserted by the DCE to indicate it is operational.
- DCD — Data Carrier Detect; asserted by the DCE when a carrier signal is detected on the line.
- DTR — Data Terminal Ready; asserted by the DTE to indicate it is powered and ready.
- TxC — Transmit Clock; clock signal provided by the DCE for synchronous transmit timing.
- RxC — Receive Clock; clock signal provided by the DCE for synchronous receive timing.
- TxCE — Transmit Clock External; clock sourced from the DTE for loopback or external timing modes.
- LL/DCD (J1-44) — Local Loopback control signal on the DTE side; maps to LTST (Local Test) at J2-18 on the DB-25.
- Circuit GND — Signal ground reference for all circuits.
- Shield GND — Cable shield drain connected to chassis/frame ground.
- MODE_0 / GND / MODE_DCE — Shorting group on the DB-60 that selects the EIA/TIA-232 interface type and DTE mode; not connected to the DB-25 end.