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Help - Mitsubishi Meldas 600 DNC Drip Feed


Apr 30, 2021
Hi all,

A brief summary before I get into more detail:

I need to run programs via drip feed on an OKK HM-50S with a Meldas 600 series controller but I get a PR0460 Tape I/O Error as soon as I hit cycle start.


A few days ago I was tasked with getting a machine my company recently purchased up and running. The problem? I'm an IT guy by trade so I have literally 0 experience with CNC lathes/mills. Cue a few days of pouring through old manuals and 10 year old forum threads and I've managed to establish communication with the machine from a laptop via RS-232-C using dnc4U. I can both send and receive programs over RS-232-C but now I'm dealing with programs that are too large to fit into memory so I need to get drip feed working.

The machine is an OKK HM-50S with a Mitsubishi Meldas 600 series controller. My machine parameters are as follows:

Data Input Port No: 1
Data Output Port No: 1
NC oper port No: 1
NC oper dev No: 1
Macro print port No: 0
Macro print dev No: 3
9600 Baud Rate
8 Data bits
2 stop bits
1 parity bit
Even Parity
RTS/CTS Handshake

I've matched the dnc4u parameters to the machine parameters and set the data transfer mode to drip feed

My Process:
1) Change to remote(tape) mode on the machine
2) Enable Single Block Mode
3) Hit the Monitor button
4) Select Operation Search
5) Change the device to RS232
6) Enter O([Program #]) N() B()
7) Hit Input Calc
8) Hit Cycle Start

As soon as I hit Cycle Start I get a PR0460 Tape I/O Error. I don't even get a chance to send data from the laptop. I've tried to start sending data before I hit Cycle start to the same result.

Anyone familiar with Meldas controllers know what I'm doing wrong?


Apr 30, 2021
You think so? Even though I can already communicate and transfer programs? Does drip feed require a separate pin arrangement from regular communication on most machines?