Wiring Spec Mirrored from :http://www.sunhelp.org/unix-serial-port-resources/serial-pinouts/ which it not always up.

Port voltage:

Many Sun cpu serial ports can be configured as either RS-232 (+/- 12V) or RS-423 (+/- 5V). Defaults vary. See the hardware documentation for your machine to locate the jumper to configure this, if it exists. Most implementations do not have to worry about the voltage on the serial port.

Port splitter cable:

Many Suns need a Y-cable to split the A/B Serial Port into the 2 different devices. Different Suns use different splitter cables for this purpose. Some Suns use small, round Mini DIN8 connectors that require an adapter to connect to a DB25 device, like a modem or terminal. Pinouts are shown below.

Serial Port & Cable Pinouts

ELC/SLC
Enterprise 150/ 220R/ 250/ 3000/ 3500/ 4500/ 5000/ 5500/ 6500
Enterprise 420R
Enterprise 450
IPC/IPX
Netra ft 1800
Netra t 1120/ 1125/ 1400/ 1405
Netra t1 Model 105/ AC200/ DC200
Netra X1/ 1280
Netra 240
Sparc 4, 10, 20, LX, Classic, Classic X
SPARCstation 2
SPARCstation 5
Sun Blade 100/ 150
Sun Blade 1000/ 2000
Sun Fire 280R
Sun Fire 880/ 3800/ 4800/ 6800
Sun Fire V100/ V120/ V480/ V1280
Sun Serial Parallel Controller (SPC)
Sun StorEdge T3 Disk Tray, T3B/T3+/Sun StorEdge 3900/6900
Ultra 1/ 2/ 30/ 60
Ultra 5/ 10
Ultra 80
Null modem, DB25-DB25
Null modem, DB25-DB9
Null modem, DB9-DB9
Null terminal, DB25-DB25
Null terminal, DB9-DB9
Null terminal, DB25-DB9
Keyboard, mouse, video, non-Sun pinouts

Sun ELC and SLC CPU serial ports:[Pin ID]
The Sun part number is for the ELC serial port splitter cable is X985Q. The SLC serial port splitter cable is Sun part # 530-1667. The pinout below is from the May 1993 Sun FE Handbook.

Pin  Signal  Port       Pin  Signal  Port
2    TD      A          13   CTS     B
3    RD      A          14   TD      B
4    RTS     A          15   TC      A
5    CTS     A          16   RD      B
6    DSR     A          17   RC      A
7    GND     A          19   RTS     B
8    DCD     A          20   DTR     A
12   DCD     B          24   TCO     A


SPARCstation 2:[Pin ID] The SPARCstation 2 has 2 DB25, 25-pin serial ports:

Pin Signal  Description
2   TxD     output
3   RxD     input
4   RTS     output
5   CTS     input
6   DSR     input
7   GND
8   DCD     input
20  DTR     output


Ultra 1/ 2/ 30/ 60, Enterprise 150/ 220R/ 250/ 3000/ 3500/ 4500/ 5000/ 5500/ 6500, Netra t 1120/ 1125/ 1400/ 1405, SPARCstation 5: [Pin ID] These machines have 2 DB25, 25-pin RS-423/RS-232 serial ports:

Pin   Signal      Description
2     TxD output  Transmit Data
3     RxD input   Receive Data
4     RTS output  Request to Send
5     CTS input   Clear to Send
6     DSR input   Data Set Ready
7     GND         Ground
8     DCD input   Data Carrier Detect
9-14  none        Not connected
15    TRxC input1 Transmit Clock input1

16    none        Not connected
17    RTxC input2 Receive Clock2
18-19 none        Not connected
20    DTR output  Data Terminal Ready
21-23 none        Not connected
24    TxC output3 Transmit Clock output3
25    none        Not Connected

Notes:
1 Enterprise 6500/5500/4500/3500/3000 labels this as DB. 2 Enterprise 6500/5500/4500/3500/3000 labels this as DD. 3 Enterprise 6500/5500/4500/3500/3000 labels this as DA.


Enterprise 420R: [Pin ID] This machine has 2 DB25, 25-pin RS-423/RS-232 serial ports:

Pin    Signal        Description
2      TxD output    Transmit Data
3      RxD input     Receive Data
4      RTS output    Request to Send
5      CTS input     Clear to Send
6      DSR input     Data Set Ready
7      GND           Ground
8      DCD input     Data Carrier Detect
9      BUTTON_POR    To be determined
10     BUTTON_XIR_L  To be determined
11     +5Vdc         +5 VDC
12-14  none          Not connected
15     TRxC input    Transmit Clock
16     none          Not connected
17     RTxC input    Receive Clock
18-19  none          Not connected
20     DTR output    Data Terminal Ready
21-23  none          Not connected
24     TxC output    Transmit Clock
25     none          Not Connected


Ultra 5/ 10: [Pin ID] Port A is a DB25, Port B is a DB9:

Serial Port A (DB25)
Pin   Signal      Description
2     TxD output  Transmit Data
3     RxD input   Receive Data
4     RTS output  Request to Send
5     CTS input   Clear to Send 
6     DSR input   Data Set Ready
7     GND         Ground       
8     DCD input   Data Carrier Detect
9-14  none        Not connected     
15    TRxC input  Transmit Clock   
16    none        Not connected
17    RTxC input  Receive Clock
20    DTR output  Data Terminal Ready
21-23 none        Not connected
24    TxC output  Transmit Clock
25    none        Not Connected

Serial Port B (DB9)
Pin   Signal      Description
1     CD          Carrier Detect
2     RD          Receive Data
3     TD          Transmit Data
4     DTR         Data Terminal Ready
5     GND         Ground
6     DSR         Data Set Ready
7     RTS         Request to Send
8     CTS         Clear to Send
9     RI          Ring Indicator


Netra ft 1800: [Pin ID]
The Netra ft 1800 has 1 female DB25 Console Port, 1 female DB25 Modem Port, and 1 female DB9 Remote Control Processor (RCP) Port.

Modem port (DB25)

Pin     Signal
1       Ground
2       TxD  
3       RxD 
4       RTS
5       CTS
7       SREF (Signal Reference)
8       DCD                   
20      DTR                  
Shield  Ground              
				   
Console port (DB25)
Pin     Signal  Description
1       GND     Chassis Ground
2       TxD     Output Data
3       RxD     Input Data
7       SREF    Signal Reference
Shield  —      Chassis Ground

RCP port (DB9)
Pin     Signal
2       TxD
3       RxD
5       SREF (Signal Reference)
Shield  Ground


Netra X1, 1280, t1 Model 105/AC200/DC200, Sun Fire V100/ V120/ V480/ V1280: [Pin ID] These machines have RJ45 connectors for serial ports.

Modems: The V100 and V120 have no DCD line on their serial ports, but they map DSR to DCD on at least port B. (Strange, but true). We do not believe that you can put a modem on the Netra X1, 1280, t1 Model 105/AC200/DC200, or Sun Fire V480 or V1280.

Configure the modem cable on Port B with the pinout shown to the right.

Sun InfoDoc 47436, available via login to contract customers only, at sunsolve.sun.com has a bit more information on setting up a modem for the V100/V120.

Signal         RJ45      DB25 Modem
RTS            1    —   4
DTR            2    —   20
TXD            3    —   2
Signal Ground  4    —   1
Signal Ground  5    —   7
RXD            6    —   3
DSR(DCD)       7    —   8
CTS            8    —   5

On the Netra X1 and Sun Fire V100, Port A LOM is dedicated to the Lights Out Management (LOM) device in the server. The Netra 1280/Sun Fire V1280 machines reserve port B for some non-user use. Only use port A.

One of this site’s readers says that the Cisco Modem RJ45 - DB25 adapter works just fine as a replacement for the Sun adapter with a terminal on the console port of an X1. It probably works well with the other systems listed in this section, too. The Cisco adapter is light grey, embossed with MODEM CAB-5MODCM on one side and 29-0881-01 on the other.

RJ45 - DB25 RS232 serial converter cable, RJ45 - DB9 serial cable: Below are pinouts for an RJ45 - DB25 RS232 serial converter cable, part number 530-2889-01 and a RJ45 - DB9 serial cable, part number 530-3100-xx. (There is also an unknown part number which has the same pinout except that the RJ45 BODY (black) is wired to RS232 pin 1 GND.)

Note that these are wired DCE. If you use the supplied RJ45 to DB25 RS232 adapter, you get a null-modem cable, suitable for a terminal connection.

Machine            Sun serial DB25              Machine            DB9 adapter
RJ45               RS-232 adapter               RJ45               RS-232 Pin
Pin                part # 530-2889-01           Pin                part # 530-3100-xx
1 (RTS) blue   — 5  (CTS)                     1 (RTS) blue   — 8 (CTS)
2 (DTR) orange — 6  (DSR)                     2 (DTR) orange — 6 (DSR)
3 (TXD) black  — 3  (RXD)                     3 (TXD) black  — 2 (RXD)
4 (GND) red    — 7  (GND)                     4 (GND) red    — 5 (GND)  
5 (GND) green  — 7  (GND)                     5 (GND) green  — 5 (GND)
6 (RXD) yellow — 2  (TXD)                     6 (RXD) yellow — 3 (TXD)
7 (DSR) brown  — 20 (DTR)                     7 (DSR) brown  — 4 (DTR)
8 (CTS) gray   — 4  (RTS)                     8 (CTS) gray   — 7 (RTS)


V100 - Xylogics Remote Annex 4000 Series: A reader sent us this pinout for connecting a Sun V100 to a Xylogics Remote Annex 4000 Series. (This cable pinout will connect the Annex to the RSC card on any Enterprise and Sun Fire level servers as well as the V440. It’s not just for the V100.)

Check the signal names and pin numbers for the port on your Annex model, because the pinouts vary. Match the signal names to determine your wiring needs.

V100 LOM RJ45      ANNEX RJ45
Pin  Signal        Pin  Signal
8    CTS     —   1    RTS
7    DSR     —   2    DTR
6    RXD     —   3    TXD
4    GND     —   6    GND
3    TXD     —   5    RXD
2    DTR     —   7    DSR
1    RTS     —   8    CTS


Vx Series Servers - Avocent CPS-810/1600 series console servers: A reader sent us this pinout for connecting Sun Vx Series Servers to Avocent CPS-810/1600 series console servers.

Adaptor Part # 210105, 10′ Reversing Cable Part # 690226

The following diagram shows the pinout for a CPS flatwire to SUN serial RJ45 connection; it can be used to create a custom adaptor cable between the units. This should work on all SUN servers with an RJ45 serial connection.

CPS                        SUN 
Pin  Signal                Pin  Signal
1    RTS   ————    8    CTS
2    DSR   ————    2    DTR
3    CD    –Not Used–    4    GRND
4    RD    ————    3    TD
5    TD    ————    6    RD
6    GRND  ————    5    GRND
7    DTR   ————    7    DSR
8    CTS   ————    1    RTS

Sun StorEdge T3 Disk Tray: [Top of Page] (This information is reprinted from the Sun StorEdge T3 Disk Tray Installation, Operation, and Service Manual.)
Pin  Function
1    Ground
2-3  Reserved
4    Ground
5    RXD
6    TXD

The controller card has an RS-232 serial port connector (RJ11-6). A standard serial cable is used to connect the controller service interface to a dumb terminal or computer serial port with terminal emulation.

Note: The serial port is reserved for special service procedures that can be performed only by qualified, trained service personnel. Do not attempt to perform any procedures through the serial port or you risk damaging the disk tray configuration and data.

T3B/T3+/Sun StorEdge 3900 and 6900: To connect an external serial terminal to the Storage Service Processor, use the Sun-supplied RJ45-DB9 DTE adapter, part number 530-3100-01, pinout as described in the Netra X1 link on this page, according to the Sun StorEdge 3900 and 6900 Series 1.1 Reference and Service Manual. For other connections to this device, see that Sun document.

Sun IPC and IPX CPU serial ports: [Pin ID]
Sun no longer sells the serial DIN8 to DB25 serial cable part. It’s available for about US$28 from Ultra Spec Cables.

Macintosh serial cables may also work for terminal connections (if lines 2 and 3 are crossed, as in a null-modem cable), but not for modem connections, since the Macintosh cable has no DCD line. There are several different Mac modem cables, so check that the pinout matches what you need.

Note that DB25 pin 6, 15, 22, 24, and 25 are not supported on the Sun serial port adapter cable. The left pinout below is taken from the SPARCstation IPC Installation Guide.

IPC & IPX DB25 to DIN8 Cable Pinout

DIN8   DB25    Signal  Description
Pin    Pin
—-   —-    ——  ———–
1      20      DTR     Data Terminal Ready
2      5       CTS     Clear to Send
3      2       TXD     Transmit Data
4      7       GND     Ground
5      3       RXD     Receive Data
6      4       RTS     Request to Send
7      8       DCD     Data Carrier Detect
8      17      RTXC    Receive Clock
N/A    6       DSR     Data Set Ready, not used
N/A    15      DB      Transmit Clock, not used
N/A    22      RI      Ring Indicator, not connected
N/A    24      DA      Transmit Clock, not used
N/A    25      -       Not connected

Mini DIN8 MacintoshPlus Serial Cable Pinout
(One of many Mac serial cables. Not all will work.)



Pin  Signal      Description
—  ——      ———–
1    HSKo        Output Handshake
                 (Zilog 8530 DTR pin)
2    HSKi/CLK    Input Handshake 
                 OR External Clock
3    TxD-        Transmit data (-)
4    Ground      Signal ground
5    RxD-        Receive data (-)
6    TxD+        Transmit data (+)
7    N/C         (no connection)
8    RxD+        Receive data (+)

Sun Sparcstation 4, 10, 20, LX, Classic, Classic X, & Enterprise 450 CPU serial ports:
Y-cable (Sun Part number X985A) and the DB25 connector on the system unit, labeled A/B.

Reprinted from the Sun Microsystem Inc.’s Desktop SPARC Hardware Owner’s Guide (Dec ‘92) and other information. This is the pinout of the Serial Port A/B connector and the Ports A and B of the Y-Cable that attach to it.

Legend: x = active pins, o = inactive pins (or pin not there)

E450 tidbit: The E450 has its serial port set to RS-423 (+/- 5v) by default. To change it to RS-232 (+/- 12v), move the jumper at J3303 (near the parallel port) from pins 2-3 to pins 1-2. This is seldom necessary with modern serial devices, because most devices can use either voltage set. But, there are those rare times when some strange device cares about the serial port voltage.

Sun Sparcstation 4, 5, 10, 20, LX, Classic, Classic X & Ultra Enterprise 450: [Pin ID]
System Unit Back Panel Serial Connector Pinout

    1  1  1  1                   
    3  2  1  0  9  8  7  6  5  4  3  2  1
  —————————————–
  \ x  x  x  o  o  x  x  x  x  x  x  x  o /
   \ x  x  o  o  o  x  x  x  x  x  x  x  /
    ————————————-
     2  2  2  2  2  2  1  1  1  1  1  1
     5  4  3  2  1  0  9  8  7  6  5  4

Pin    Circuit  Signal  Direction  Description/Port
—    ——-  ——  ———  —————-

1      none     none    —         not connected
2      BA       TD      output     Transmit Data/A
3      BB       RD      input      Receive Data/A
4      CA       RTS     output     Request to Send/A
5      CB       CTS     input      Clear to Send/A
6      CC       DSR     input      Data Set Ready/A
7      AB       SG      —         Signal Ground
8      CF       DCD     input      Data Carrier
                                   Detect/A
9-10   none     none    —         not connected
11     SCD      SDTR    output     Data Terminal 
                                   Ready/B
12     SCF      SDCD    input      Data Carrier 
                                   Detect/B
13     SCB      SCTS    input      Clear to Send/B
14     SBA      STD     output     Transmit Data/B
15     DB       TC      input      Transmit Clock/A 
                                   DCE source
16     SBB      SRD     input      Receive Data/B
17     DD       RC      input      Receive Clock/A
18     SDB      STC     input      Transmit Clock/B
19     SCA      SRTS    output     Request to Send/B
20     CD       DTR     output     Data Terminal 
                                   Ready/A
21-23  none     none    —         not connected
24     DA       TC      output     Transmit Clock/A 
                                   DTE source
25     DA       TC      output     Transmit Clock/B 
                                   DTE source
Sun Sparcstation 4, 5, 10, 20, LX, Classic, Classic X & Ultra Enterprise 450:
Serial Interface Y-Cable Port A Specifications - Synchronous & Asynchronous
    1  1  1  1                   
    3  2  1  0  9  8  7  6  5  4  3  2  1
  —————————————–
  \ o  o  o  o  o  x  x  x  x  x  x  x  o /
   \ o  x  o  o  o  x  o  o  x  o  x  o  /
    ————————————-
     2  2  2  2  2  2  1  1  1  1  1  1
     5  4  3  2  1  0  9  8  7  6  5  4

Pin  Circuit  Signal  Direction  Description
—  ——-  ——  ———  ———–

2     BA      TD      output     Transmit Data
3     BB      RD      input      Receive Data
4     CA      RTS     output     Request to Send
5     CB      CTS     input      Clear to Send
6     CC      DSR     input      Data Set Ready
7     AB      SG      —         Signal Ground
8     CF      DCD     input      Data Carrier
                                 Detect
15    DB      TC      input      Transmit Clock, 
                                 DCE source
17    DD      RC      input      Receive Clock
20    CD      DTR     output     Data Terminal
                                 Ready
24    DA      TC      output     Transmit Clock, 
                                 DTE Source

Sun Sparcstation 4, 5, 10, 20, LX, Classic, Classic X & Ultra Enterprise 450:
Serial Interface Y-Cable Port B Specifications - Asynchronous Only

    1  1  1  1                   
    3  2  1  0  9  8  7  6  5  4  3  2  1
  —————————————–
  \ o  o  o  o  o  x  x  o  x  x  x  x  o /
   \ o  o  o  o  o  x  o  o  o  o  o  o  /
    ————————————-
     2  2  2  2  2  2  1  1  1  1  1  1
     5  4  3  2  1  0  9  8  7  6  5  4


Pin  Circuit  Signal  Direction  Description 
—  ——-  ——  ———  ———– 
2    BA       TD      output     Transmit Data
3    BB       RD      input      Receive Data
4    CA       RTS     output     Request to Send 
5    CB       CTS     input      Clear to Send
7    AB       SG      —         Signal Ground
8    CF       DCD     input      Data Carrier
                                 Detect
20   CD       DTR     output     Data Terminal
                                 Ready

Ultra 80 / Sun Blade 1000 / Sun Blade 2000 / Sun Fire 280R CPU serial ports: [Pin ID]
The serial port A and B connectors are DB25 connectors located on the motherboard back panel. The 2 ports are wired in the same way.

Pin    Signal             Description
—    ——             ———–
1      NC                 Not connected
2      SER_TDX_A_CONN     Transmit data
3      SER_RXD_A_CONN     Receive data
4      SER_RTS_A_L_CONN   Ready to send
5      SER_CTS_A_L_CONN   Clear to send
6      SER_DSR_A_L_CONN   Data set ready
7      GND                Signal ground
8      SER_DCD_A_L-CONN   Data carrier detect
9      BUTTON_POR         Power-on reset
10     BUTTON_XIR_L       Transmit internal
                          reset
11     +5VDC              +5 VDC
12-14  NC                 Not connected
15     SER_TRXC_A_L_CONN  Transmit clock
16     NC                 Not connected
17     SER_RXC_A_L_CONN   Receive clock
18-19  NC                 Not connected
20     SER_DTR_A_L_CONN   Data terminal
                          ready
21-23  NC                 Not connected
24     SER_TXC_A_L_CONN   Terminal clock
25     NC                 Not connected

Sun Blade 100 / 150 CPU serial port: [Pin ID]
The 1 serial port connector is a DB9 type connector located on the backpanel. The serial port connector provides asynchronous serial communications.


Pin  Signal  Description
—  ——  ———–

1    CD      Carrier detect
2    RD      Receive data
3    TD      Transmit data
4    DTR     Data terminal ready  
5    GND     Ground
6    DSR     Data set ready
7    RTS     Request to send
8    CTS     Clear to send
9    RI      Ring indicator
Sun Fire 880/ 3800/ 4800/ 6800 serial ports: [Top of Page] [Pin ID]
There is one DB25 serial port connector which provides both port A and port B. Use a splitter cable (Sun part # X985A) to access port B. The serial port connector provides synchronous and asynchronous serial communications. The other ports on the 880 are described in the Sun Fire 880 Server Owner’s Guide.

Pin Signal               Pin Signal

— ——               — ——
1   No Connection        14  Transmit Data B
2   Transmit Data A      15  Transmit Clock A
3   Receive Data A           (External)
4   Ready To Send A      16  Receive Data B
5   Clear To Send A      17  Receive Clock A
6   Synchronous A        18  Receive Clock B
7   Signal Ground A      19  Ready To Send B
8   Data Carrier         20  Data Terminal
    Detect A                 Ready A
9   No Connection        21  No Connection
10  No Connection        22  No Connection
11  Data Terminal        23  No Connection
    Ready B              24  Transmit Clock A
12  Data Carrier             (Internal)
    Detect B             25  Transmit Clock B
13  Clear To Send B

Sun Serial Parallel Controller (SPC): [Top of Page] [Pin ID]
This device, part numbers F501-1511 or F501-1931, uses an SBUS card to connect to a patch panel containing 8 full-duplex DB25 serial ports (RS-232 or RS-423) and 1 unidirectional Centronics parallel port. The serial ports support baud rates of 50 to 38.4K, with 135K baud total throughut. More information is available from the Sun Serial Parallel Controller User’s Guide.

DB25 Serial Ports

Pin  Signal
—  ——
1    Frame Ground
2    TXD
3    RXD
4    RTS
5    CTS
6    DSR
7    Signal Ground
8    CD
20   DTR

Netra 240 serial ports: [Top of Page] [Pin ID]
There are 2 serial ports. The RJ45 port is labeled SERIAL MGT and the DB9 port is labeled SERIAL (10101). The RJ45 SERIAL MGT port should be used only for console server management. The DB9 SERIAL (10101) port is for general purpose serial data transfers.

RJ45 SERIAL MGMT Console port

Pin Signal                 Pin Signal
— ——                 — ——
1   Request to Send        5   Ground
2   Data Terminal Ready    6   Receive Data
3   Transmit Data          7   Data Set Ready
4   Ground                 8   Clear to Send

If you need to connect to the SERIAL MGT port using a cable with either a DB9 or a DB25 connector, use the adapter supplied with the machine to perform the crossovers given for each connector. Pinouts for the adapters are given below.

RJ45 to DB9 Adapter                 RJ45 to DB25
Crossover                           Crossover

RJ45 connector   DB9 Adapter        RJ45 connector    DB25 Adapter
Pin Signal       Pin Signal         Pin Signal        Pin Signal

— ——       — ——         — ——        — —— 
1   RTS ——– 8   CTS            1   RTS ——— 5   CTS
2   DTR ——– 6   DSR            2   DTR ——— 6   DSR
3   TXD ——– 2   RXD            3   TXD ——— 3   RXD
4   GROUND —– 5   GROUND         4   GROUND —— 7   GROUND
5   GROUND —– 5   GROUND         5   GROUND —— 7   GROUND
6   RXD ——– 3   TXD            6   RXD ——— 2   TXD
7   DSR ——– 4   DTR            7   DSR ——— 20  DTR
8   CTS ——– 7   RTS            8   CTS ——— 4   RTS

DB9 SERIAL (10101) port

Pin Signal                 Pin Signal
— ——                 — ——
1   Data Carrier Detect    6   Data Set Ready
2   Receive Data           7   Request to Send
3   Transmit Data          8   Clear to Send
4   Data Terminal Ready    9   Ring Indicator
5   Ground
What next?

Have you found the serial port pinout for a Sun machine not listed here? If so, send it to the Webmaster with a pointer to the information, so we can verify it before adding it to this list.

Null Modem & Null Terminal Pinouts
Null modem pinout DB25 to DB25: [Pin ID]
Used in connecting 2 computers with full modem signalling capability. This is usually the pinout found in null modem cables for DB25 to DB25.

DB25              DB25
—–             —–
1 GND  ———- 1 GND
2 TD   ———- 3 RD
3 RD   ———- 2 TD
4 RTS  ———- 5 CTS
5 CTS  ———- 4 RTS
7 GND  ———- 7 GND
6 DSR  —+
          +—— 20 DTR
8 DCD  —+
             +— 6 DSR
20 DTR ——+
             +— 8 DCD

Null modem pinout DB9 to DB9: [Pin ID]
Used in connecting 2 computers with full modem signalling capability. This is usually the pinout found in null modem cables for DB9 to DB9.


DB9                  DB9
—                  —
3 TD   ————- 2 RD
2 RD   ————- 3 TD
7 RTS  ————- 8 CTS
8 CTS  ————- 7 RTS
5 GND  ————- 5 GND
6 DSR  —+  
          +——— 4 DTR
1 DCD  —+
               +— 6 DSR
4 DTR ———+  
               +— 1 DCD

Null modem pinout DB25 to DB9: [Top of Page] [Pin ID]
Used in connecting 2 computers with full modem signalling capability. This is usually the pinout found in null modem cables for DB25 to DB9.


DB25                DB9
—-                —

2 TD   ———— 2 RD
3 RD   ———— 3 TD
4 RTS  ———— 8 CTS
5 CTS  ———— 7 RTS
7 GND  ———— 5 GND
6 DSR  —+ 
          +——– 4 DTR
8 DCD  —+
               +— 6 DSR
20 DTR ——–+  
               +— 1 DCD

Null terminal pinout DB25 to DB25: [Pin ID]
Used in connecting 2 computers without modem signalling capability. You usually have to build this cable yourself.

DB25     DB25
—-     —-
1 GND — 1 GND 
2 TD  — 3 RD
3 RD  — 2 TD
7 GND — 7 GND

Null terminal pinout DB9 to DB9: [Pin ID]
Used in connecting 2 computers without modem signalling capability. You usually have to build this cable yourself.


DB9      DB9
—-     —
3 TD  — 2 RD
2 RD  — 3 TD
5 GND — 5 GND

Null terminal pinout DB25 to DB9: [Pin ID]
Used in connecting 2 computers without modem signalling capability. You usually have to build this cable yourself.


DB25     DB9
—-     —
2 TD  — 2 RD
3 RD  — 3 TD
7 GND — 5 GND