Hi,ALL:


Our CNC machine controller is Mitsubishi Meldas 520am(very old), PC operation system is Windows XP. RS232 connection: CNC Machine---25pin---25 pin---converter---9pin---PC. My RS232 line is connected like the following:
PC CNC
1---------------------- 1
3 ---------------------- 2
2 ---------------------- 3
7 ---------------------- 7
6-8-20 6-8-20
4-5 4-5

I have no problem to send very very small NC programs to CNC machine using ConnectCNC.( Using Xon/Xoff flow control, baud rate 4800, data bits:7, stop bits:2, parity: even). Since the memory at machine side is very small (less than 100k), I try to use DNC, but don't succeed, with error "P460 TAPE I/O ERROR". ConnectCNC does not seem to care about whether the CNC machine is ready for receiving or not, and it just sends the NC program after the SEND button is pressed. It never waits for a Xon singal.

The funning thing is that the machine can't receive a small NC program when I use " Wait for Xon" function in other software such as Cimco edit (same settings as ConnectCNC on both PC and machine sides).

so my stupid questions are:
Is the Meldas 520 using the same port for data receiving and sending?(There is only one port on machine).
Which handshake is better for this old machine( Xon/Xoff or hardware handshake or no handshake)?

Any suggestion will be appreciated.

Thanks in advance.

you can try, " CncSimulator Ver 4,44f (2,7 Mb) "can download free version . http://www.cncsimulator.com
25 pin------------------9pin

1+7---------------------- 5
3---------------------- 3
2 ---------------------- 2
4---------------------- 8
5-----------------------7
6-8-20 jumper 1-4-6
Using Xon/Xoff flow control, baud rate 4800,data bits:7, stop bits:2, parity: even

Are you using a laptop with a USB to Serial adapter? I've had problems with these trying to use XON/XOFF handshaking.

i am not using a laptop. i used standerd pc with 9 pin Serial port direct to machine side 25 pin Serial port.