HEIDENHAIN TNC 335 Technical Manual - Manual (Page 523)

8-16
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 and (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 exactly 50 times. This is
followed by the individual program blocks, which each end with the characters and .
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 (XOFF), continuing transfer
by sending character (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.