The Heidenhain TNC 425 control offers versatile RS232 data transfer capabilities. By supporting standard XOn/XOff software handshaking and the proprietary Heidenhain blockwise communication protocol, it ensures robust DNC connectivity. This is critical for reliable drip-feeding, allowing large programs to execute directly from a PC. Accurate configuration of the Machine Parameters (MP) is essential to maintain a stable serial link and prevent framing errors or data loss. Common pitfalls include baud rate mismatches, incorrect parity settings, or conflicting handshaking configurations; always verify that the PC software settings perfectly mirror the control’s hardware parameters. Ensuring the cable is shielded and correctly wired for software flow control is equally vital for avoiding communication timeouts during high-speed data transmission.
| Parameter | Value | Comments |
|---|---|---|
| Interface | EXT 2 | - |
| Baud Rate | 2400 | 7 data bits, even parity, 2 stop bits |
| MP 5200.1 | 2 | - |
| MP 5201.1 | 3 | - |
| MP 5020.1 | 104 | 7 data bits, even parity, 2 stop bits, DC code (XOn/XOff) |
| MP 5030.1 | 0 | Blockwise disabled (1 = enabled) |
Cabling and Protocols
For standard transmission without the blockwise protocol, flow control must be set to XOn/XOff. In your DNC software, configure STX (02) as the start code and ETX (03) as the end code for correct data packet identification.
When using the blockwise protocol (MP5030.1 = 1), reliable transmission is maintained even for extremely large files, preventing buffer overflows.
The cable illustrated is optimized for use with software flow control and the Heidenhain blockwise transmission protocol.