I just got in my first CNC it is a 1998 VF-1. I got the electric run to it and im ready to start programming! I don't have the cable that im going to run from my comp to the machine and im not exactly sure what to buy. I can take a photo of the connecter and go to my local computer shop but what else do I need to know. What size cable for sure and also is there anything else that I should be asking for?
The term Null Modem is a generic term and applies to any cable where the corresponding TX and RX lines are swapped. There are three basic Null Modem cable configurations:
1. Full Handshake
2. Software Handshake (Xon Xoff)
3. No Handshake
Most commonly a Software Handshake configuration is used and the pin out is as follows:
Machine Side ---------------------------- PC Side
DB25 Male ----------------------------- DB9 Female
1 ---- Shield Trace ------------------ Not Connected
2 ----------------------------------------- 2
3 ----------------------------------------- 3
4
| Bridged
5
6
|
8 All Bridged
|
20
7 ----------------------------------------- 5
As can be gleaned from the above, a cable having only three wires, plus a trace wire and shield is required. The Trace wire is a bare wire running the full length of the cable and in contact with the shield. The Shield, via the Trace wire, should only be connected at the control side. Connecting the Shield at both ends may result in a Ground Loop if the machine and PC don't share the same Protective Ground, or if either is not Grounded well.
The Settings at the Machine and the PC must match. The protocol to use for Xon Xoff and XModem Handshaking are as follows:
Machine Control Settings for Xon Xoff Handshaking
11 Baud Rate (9600) - Starting Point
12 Parity (Even)
13 Stop Bits (1)
14 Synchronization Xon/Xoff
24 Leader to Punch (None)
25 EOB Pattern (CR LF)
37 Number Data Bits (7)
Machine Control Settings for XModem Communication
11 Baud Rate Select: 19200
12 Parity Select: NONE
13 Stop Bits:1
14 Synchronization: XMODEM
37 RS-232 Data Bits: 8
Either Protocol can be used; however, XModem is recommended for DNC applications. A Check Sum is done and if the sent and received data don't agree, the control will halt, avoiding a crash if the dropped character happened to be part of a coordinate.
The settings at the PC have to match those of the control.
Regards,
Bill