HEIDENHAIN TNC 335 Technical Manual - Manual (Page 523)

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TNC 360 2 TNC data interfaces 8/95
These transmission protocols can be selected in three different operating modes, as follows:
– ME Standard transmission protocol to match HEIDENHAIN
magnetic tape unit (7 data bits, 1 start bit, 1 stop bit)
Data transmission rate: 2400 baud
– FE Transmission with Block Check Character and with fixed control
characters (7 data bits, 1 start bit, 1 stop bit)
Freely configurable baud rate
– EXT Freely configurable operating modes: data format, transmission
protocol and control characters can be freely set via machine
parameters. Freely configurable baud rate.
The following applies to data transmission protocols:
– If a file which is read in is already stored in the TNC, is displays the message
"ERASE=ENT / OVERREAD=NOENT".
In this case the TNC aborts transmission with the appropriate handshake and does not continue
transfer until after acknowledgment.
In the event of an attempt to erase write-protected files, the error message "PROTECTED PGM" is
displayed and the dialog "OVERREAD=ENT/END=NOENT". In this case, either the next file can be
read in or the transfer can be aborted.
– If a file has been read out and the data transfer menu has been terminated with the END key,
the TNC outputs characters <ETX> and <EOT> (or ASCII characters according to setting in
MP5010 in operating modes EXT).
– If a transmission is terminated with the END-key, the error message "PROGRAM INCOMPLETE" is
issued.
2.4.1 Standard transmission protocol
With this protocol, first of all the TNC transmits the character <NUL> exactly 50 times. This is
followed by the individual program blocks, which each end with the characters <CR> and <LF>.
These blocks are transmitted in order, but they are not error checked. If the receiver's data buffer is
full, the receiver has two alternatives for stopping and recommencing transmission:
– Software handshake - Stopping transfer by sending character <DC3> (XOFF), continuing transfer
by sending character <DC1> (XON).
– Hardware handshake - By putting appropriate voltage level on the RTS and CTS control and signal
lines of the RS-232-C/V.24 interface.