Cksh (Checksum High) And Cksl (Checksum Low); Bcc (Block Check Character) - Hitachi 902 Service Manual

NOTES:
1.

BCC (Block Check Character)

The RS-232C communication program is provided with a function to add BCC to
the send text and support BCC check of the receive text for detection of an
improper message.
• Condition (1):
• Condition (2):
At this time, BCC accumulation is started from the character following STX and
carried out until ETX appears.
[Calculation Method]
Dn = n-th character in hexadecimal notation (1 byte)
BCC = Block check character (1 byte)
BCC = D1 + D2 + D3 + Dj + ...Dn + (ETX)
(+: Exclusive OR)
2.

CKSH (checksum high) and CKSL (checksum low)

The checksum is calculated by adding all characters between the frame
character and the final character in the data field (one character before end-of-
data code), and the lower two digits of the calculated checksum are converted
to the ASCII code.
Example:
The start-of-text character is STX (02)
text character is ETX (03)
The text data consists of characters (nontransparent
mode).
16 - 3
16
.
16
16
and the end-of-