Denso BHT-7500 - Manual (Page 204)

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[ 3 ] BCC for Horizontal Parity Checking
To check whether data has been transmitted accurately, the BHT supports horizontal
parity checking for every transmission block.
In horizontal parity checking, a horizontal parity byte so called BCC (Block Check
Character) is suffixed to an ETX of every transmission block.
In the BHT-protocol, every parity bit of BCC is set so that all set bits at the same bit
level (including a parity bit) in the characters contained in the transmission block have
an even number by binary addition, excluding SOH, STX, and functions SOH$ and
STX$.
(For details about SOH$ and STX$ which are protocol functions unique to BHT-BASIC,
refer to the "BHT-BASIC Programmer's Manual.")
b7
b0
Character
(Vertical parity)
Horizontal parity byte
(BCC)
[ For 8-bit data ]
Shown below is a data text block indicating the bits to be added for horizontal parity
checking.
To be added for
horizontal parity
checking
Serial
number
Data text