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Home > RS232 Pin Connection Reference Diagrams

Use this page as a reference if making your own cables or for checking existing cables. It is not always necessary to make your own cable, you can buy pre-made cables from us for all CNC machine tools.

Tips: Never connect a CNC's serial port to a parallel (printer) port or to a network port.
If computer lacks serial port, a USB to serial port adapter may be used.
Configurations shown are the most commonly implemented, we are not trying to imply that alternative configurations will not work.

For assistance with your application, please call 1-805-383-2492.

Note: Diagrams are for reference use only.

 

Figure 1. DB9F to DB25M, NULL Modem (Crossover)

 

Figure 2. DB25F to DB25M, NULL Modem (Crossover)

 

Figure 3. DB9F to DB25M, Straight
 (Yes, pins 2 and 3 are crossed, but it's still a straight connection because TD is connected to TD...)

 

Figure 4. RS232C PC Pin Assignments
 Actual male connector on chassis of PC

Pin (DB9) Signal Function Label I/O Type
1 Carrier Detect CD Input
2 Receive Data RD Input
3 Transmit Data TD Output
4 Data Terminal Ready DTR Output
5 Signal Ground SG ---
6 Data Set Ready DSR Input
7 Request to Send RTS Output
8 Clear to Send CTS Input

 

Figure 5. RS232C PC Pin Assignments
 Actual male connector on chassis of PC

Pin (DB25) Signal Function Label I/O Type
1 Protective Ground PG ---
2 Transmit Data TD Output
3 Receive Data RD Input
4 Request to Send RTS Output
5 Clear to Send CTS Input
6 Data Set Ready DSR Input
7 Signal Ground SG ---
8 Carrier Detect CD Input
20 Data Terminal Ready DTR Output

 

Figure 6. RS232C CNC Pin Assignments
 Actual female connector on cabinet of CNC

Pin (DB25) Signal Function Label I/O Type
1 Protective Ground PG ---
2 Transmit Data TD Output
3 Receive Data RD Input
4 Request to Send RTS Output
5 Clear to Send CTS Input
6 Data Set Ready DSR Input
7 Signal Ground SG ---
8 Carrier Detect CD Input
20 Data Terminal Ready DTR Output

 

 

Figure 7. DB25 to  EIA/TIA 561 (RJ45) Modular Adapter (PC or CNC Side)
 Use to send RS232 over EIA/TIA 568A CAT5 Ethernet cable.
Add separate NULL modem adapter (Radio Shack Cat # 26-1496) to this adapter on CNC side.
NEVER use modular adapter to connect a DB serial port to a 10BaseT Ethernet network port!
ALWAYS use modular adapters in pairs!

DB25 Pin Hole Wire Color RJ45 Pin
1

---

---
2 Green 5
3 Yellow 6
4 White* 8
5 Brown 7
6 Blue 1
7 Red 4
8 Orange 2
20 Black 3

*Or Gray

 

Figure 8. DB9 (DE9) to  EIA/TIA 561 (RJ45) Modular Adapter (PC Side)
Use to send RS232 over EIA/TIA 568A CAT5 Ethernet cable.
NEVER use modular adapter to connect a DB serial port to a 10BaseT Ethernet network port!
ALWAYS use modular adapters in pairs!

DB9 Pin Hole Wire Color RJ45 Pin
1 Orange 2
2 Yellow 6
3 Green 5
4 Black 3
5 Red 4
6 Blue 1
7 White* 8
8 Brown 7
9 --- ---

*Or Gray

 

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Last Updated:10/27/2005