HEIDENHAIN TNC 335 Technical Manual - Manual (Page 536)

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TNC 360 3 Standard Data Transmission Protocol 8-29
3 Standard Data Transmission Protocol
3.1 General information
This protocol is set as standard in operating mode ME and can also be optionally selected for
operating modes EXT via the machine parameters. In the following, the control characters which are
sent and received with this protocol are listed for the various transmission alternatives. When
outputting a file, the character is sent exactly 50 times at the start of the file. When reading
in, however, the control unit ignores this character. Therefore it is of no importance how often the
peripheral unit sends the character before the file.
If, however, ME mode is set instead of EXT, attention must be paid to the following:
All the programs in a file which end with the end-of-text character are stored in the magnetic
tape unit ME. The ME transmits this file with all the programs to the control unit. The TNC then
selects the appropriate program and stores it.
A further important difference between EXT mode in the standard protocol and ME mode is that the
character is never sent in ME mode because the magnetic tape unit is incapable of
processing this character.
In this protocol, if an error is to be signaled to the TNC, the following sequence of instructions must
be sent:
<1> 'ERROR NUMBER'
Listed below are the transmission protocols for the various alternatives for data output and input.
EXT mode is set:
– Control character for "End of Text" -
– Control character for "End of Transmission" -
– Software handshake
3.1.1 Calling the program directory
Using the menu item "Program Directory", the list of file names can be requested from an external
memory and displayed in the TNC.
If the external directory is requested, the TNC sends control character .
If the request is immediately interrupted with the END key, the TNC sends characters
and no directory is read in.
If the request is not interrupted, the peripheral unit sends all of the external programs in order. Their
names are then shown in the TNC.