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Getting Started Sending And Receiving

If you have connected DNC software systems between your CNC machine and your computer then you don't really need to read this.

If you haven't then this is what we usually do. First select a CNC from our predefined list.

Then decide on the type of cable you should use. The vast majority of CNC will use a standard type of cable. These can roughly be broken down into those that use hardware handshaking and software handshaking.

Hardware Handshaking
If your CNC uses hardware handshaking then you will have to connect more pins. Note how the handshaking pins 4 & 5 and 6 & 8 & 20 are connected. This is often called a straight through cable.

CNC Control Computer 25 Pin   CNC Control Computer 9 Pin
DB-25 Male DB-25 Male   DB-25 Male DB-9 Male
1 (Chassis ground) (Not connected)   1 (Chassis ground) (Not connected)
2 3   2 2
3 2   3 3
7 7   7 5
4 5   4 8
5 4   5 7
6 20   6 4
20 & 8 looped 6   20 & 8 looped 6

Software Handshaking
If your CNC uses software handshaking then you dont have as many pins to connect. Notice how the pins 4 & 5 and 6 & 8 & 20 are looped. This "fools" the CNC into detecting a remote device, your computer. This is often called a null modem.

CNC Control Computer 25 Pin   CNC Control Computer 9 Pin
DB-25 Male DB-25 Male   DB-25 Male DB-9 Male
1 (Chassis ground) (Not connected)   1 (Chassis ground) (Not connected)
2 3   2 2
3 2   3 3
7 7   7 5
4 & 5 looped     4 & 5 looped  
6 & 20 & 8 looped     6 & 20 & 8 looped  

The function of the pins are as follows:-

DB-25 Male     DB-9 Male  
1 Chassis Ground   1 Carrier Detect
2 Transmit Data   2 Receive Data
3 Receive Data   3 Transmit Data
4 Request To Send   4 Data Terminal Ready
5 Clear To Send   5 Signal Ground
6 Data Set Ready   6 Data Set Ready
7 Signal Ground   7 Request To Send
8 Carrier Detect   8 Clear To Send
20 Data Terminal Ready   9 (Not Connected)

Here is a quick rundown on the settings inside dncSoftware

Com Port Settings

Ports com1 to com128, baud 150 to 460800, ISO and EIA adjustable input and output buffer sizes, keepalive so that the com ports can be opened all the time or closed when not in use (some CNC always need to be able to see a remote device or they will error out)

Send Parameters

Send any CNC control codes before and after the main NC program to initiate RS232 at the CNC, all end-of-blocks supported, ignore spaces and blocks that contain any sequence of characters.


User definable block and character delays, wait for XON before sending to CNC

Receive Settings

Automatically strip everything from the CNC before a certain character and after a certain character to remove unwanted CNC control codes from the transfer and so the received file, discard codes, end of block can auto detect or you can choose which end of block to use, automatically show data being received on the fly for best visual interpretation of transfer.


Set up to 24 different folders in CNC view, so that you can segregate your files just how you want them.

Our new DNC wizard will help you quickly detect your CNC settings, so if you've lost your CNC manual you are saved!

DNC Software Ltd
Registered in England : No. 7384997
Registered Office : 3 Meynell St, Wildsworth, Gainsborough, Lincs, DN21 3DX, UK

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