Dnc problem for Mitsubishi Meldas 520AM

[koeitool]

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.

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.

[Caprirs]

Help needed to connect Mitsubishi Meldas to PC

See that link for my settings for file transfer and DNC. I use Device 0 for file transfer (Xon/Xoff) and Device 1 for DNC (hardware flow control). On the PC, I use Windows Hyperterminal for file transfers. When using DNC, set the handshake to hardware for RTS/CTS.

1. Start with the DNC software running on the PC so it "turns on" the COM port.
2. On the CNC machine, put the Mode select on DNC.
3. In the Search screen enter the program number and set the last field TAPE to "1" and press the INPUT key. The CNC will now be ready to recieve.
4. At the PC, start sending the file.
5. At the CNC, press Cycle Start to begin running the program.

[koeitool]

Hi, caprirs:

Thank you very much for your reply.

I still have some questions:

1.Do you mean that I have to use hardware handshake control for DNC?
Currently I’m using Software(Xon/Xoff) control. 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

2.Do I have to change the line link to hardware control? Maybe Meldas is special, only using Hardware control, I don’t know. I’ll give a try.

3.Can I use the same port no. for data transfer and DNC? I have only one port on my machine. I see that you are using different ports for file transfer and DNC.

4.I don’t have any DNC mode on my machine control panel. Do you mean the Tape Mode?

Your suggestion will be greatly appreciated.

[Caprirs]

1. You do not have to use hardware handshaking for DNC. However, it speeds up the transfer of the file because it allows the send/stop signals to run on wires 4 & 5 instead of being encoded on 2 & 3. Thus, 2 & 3 contain only data, no transmission signals.

Your wiring needs altering I think. Pins 2 & 3 should be crossed to each other. You show that yours are wired straight through. Pin 2 is send and 3 is receive. Your PC has to send data on 2 to the Meldas pin 3 (receive).

You also have jumpered 4 & 5 which defeats the hardware handshaking. Thus, you have to use Xon/Xoff software control with your wiring of 4 & 5.

You have 6, 8, & 20 jumpered to each other at each end. This may be why the PC starts sending without waiting for the Meldas to be ready. See the attached picture of the null modem adapter.

2. Line link? Nothing special about the Mitsubishi. Standard RS232 as far as I know.

3. You can use the same port for file transfer and DNC. I am using the same port for both. However, I am using different "devices" with different settings. Everything goes through the same DB25 connector on the machine but I use hardware handshaking for DNC.

4. Tape mode should be the same as DNC mode. The OEM machine tool builder makes the control panels so there is some variance in labels. Kinda like some machines say "Zero Return" and others say "Home".

[koeitool]

Hi, caprirs:

Thank you very much! You are an expert on RS232.

I made a mistake yesterday. Actually, my wiring is crossed at pin 2 &3 (not straight). I’m still not clear why jumpering 4 & 5 will defeat the hardware handshaking and why can’t jumper
6, 8, & 20 at both sides. I found some cable guideline on the following website. It seems jumper 6, 8, & 20 at both sides.
http://www.cimco-software.com/support_cables.php3

Best regards!

[Caprirs]

I am no expert.

Jumpering 4 & 5 defeats the hardware handshaking because the PC is jumpered to itself and the control is jumpered to itself. Pins 4 & 5 are "Ready To Send" and "Clear To Send". By jumpering, the CNC never sees the RTS/CTS signals from the PC. Same for the reverse, the PC cannot tell the CNC to start/stop transmission.

Thus, during DNC using hardware handshaking, the CNC has to send start/stop signals via the CNC's pin 4 & 5 to the PC's pin 5 & 4. When jumpered, the CNC is sending the start/stop signals to the CNC and the PC is signaling itself instead of signaling the CNC.

I think 6, 8, & 20 work similarly. Keeping all wires jumpered prevents the CNC and PC from using those wires to communicate with each other.