HEIDENHAIN TNC 306 Technical Manual - Manual (Page 429)

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TNC 406/TNC 306 2 TNC data interfaces 3/97
2.4 Data transmission protocols
The TNC enables data and files to be transferred using two different protocols (which can be
selected via the interface setup).
These transmission protocols can be selected in three different operating modes, as follows:
– FE1 Transmission with BCC (Block Check Character) and with
fixed control characters (7 data bits, 1 start bit, 1 stop bit)
Freely configurable baud rate
– EXT Standard transmission protocol: data format and control
characters can be freely set via machine
parameters. Freely configurable baud rate.
The following applies to data transmission protocols:
– If a file being read in is already present in the TNC memory, the following message is displayed:
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
and the dialog OVERREAD=ENT/END=NOENT are displayed. In this case, either the next file can
be read in or 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 and MP5011 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 (EXT mode)
With this protocol, the TNC first transmits the character 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.