HEIDENHAIN TNC 407 (243 020) Technical Manual - Manual (Page 687)

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TNC 407/TNC 415/TNC 425 2 TNC data interfaces 01.98
The software handshake is very easy to accomplish when transmitting with BCC. The receiver
transmits neither a positive () nor a negative () acknowledgement and the transmitter
waits until it receives one of these characters.
When the receive buffer of the receiver unit is ready to receive again the unit transmits another
and the transmitter resumes the data transfer.
The software handshake can also be done with the aid of the control characters and
however. If the hardware handshake (EXT1/EXT2/EXT3) was selected this is identical with the
standard data transfer and BCC transfer (see section "Freely configurable interfaces").
3.2.2 Protocols
In the following, the transmission protocols are listed for the various file input and output
possibilities. FE2 mode is set.
If an error occurs at a peripheral device, the following block must be sent to the TNC.
"Error text"BCC
Peripheral unit
"Error" BCC
Transmission path TNC
The received error message is displayed in the TNC, but can be acknowledged and erased with the
CE key.