HEIDENHAIN MANUALplus 620 Technical Manual page 1781

Block Check
Character (BCC)
January 2012
The BCC is a block check character. The BCC is added to a transfer block to
simplify error detection. During the horizontal parity check and the cyclic block
check, block check characters are calculated and added to every transferred
data block. The appended BCC is compared with a second BCC that is
calculated by the receiver. The comparison determines whether the
transmission was executed without error.
Use MP_bccAvoidCtrlChar to ensure that the BCC is not interpreted as a
control character.
On the control, 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 cannot therefore be interpreted as a control
character.
Note
You can remove this parameter from your configuration if you do not use
blockwise data transfer.
MP_bccAvoidCtrlChar
Block Check Character (BCC) is not a control character
Available from NCK software version: 597 110-01.
Format: Selection menu
Selection: TRUE
Ensures that the check sum does not correspond to a control
character
FALSE
Function not active
Default: FALSE
Access: LEVEL2
Reaction: NOTHING
9.6 Configuring the Serial Interface 1781