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8.3.3 Configuration of Interfaces
Data bits
Block Check
Character (BCC)
Hardware
handshaking
8 – 16
To configure data format and the type of handshake in the EXT1/EXT2/EXT3
operating modes (EXT3 only for the PLC):
7 7 7 7
Select machine parameter MP5020.x.
With bit 0 you determine whether transmission is to be with seven or eight
data bits. Transmission with seven bits is normally used, for printer interfacing
eight bits are required.
With bit 1 you can ensure that the BCC is not interpreted as a control
character.
On the TNC, numbers less than $20 are defined as control characters. If
calculation of the BCC produces a number less than $20, then a blank space
is sent in addition immediately before <ETB>. The BCC will consequently
always be greater than $20 and therefore cannot be interpreted as a control
character.
With bit 2 you can determine whether the TNC stops transfer from an
external device by sending an RTS signal.
n
Data output from TNC to EXT
When the receiving buffer is full, the external device resets the RTS signal.
The TNC detects that the peripheral unit receiving buffer is full at its CTS
input:
HEIDENHAIN Technical Manual TNC 426, TNC 430
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