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■ Transmission Code and Bit Order
All characters should be coded to 7- or 8-bit code for data transmission. The
standard data exchange code of the BHT is JIS 7- or 8-bit code. The transmission
bit order is LSB (Least significant bit) first.
What follows is an example for transmitting character A (41h, 01000001b) coded to
JIS 8-level code with an even parity and a single bit each for start and stop bits.
Parity bit
Stop bit
Start bit
■ Vertical Parity
A vertical parity bit is a redundancy bit which is added to every character to be
transmitted in order to check that data has been transmitted accurately. The parity
bit should be set to "1" or "0" depending upon the parity parameter setting, to make
the number of set bits in the character even or odd. The receiver counts the
number of set bits in the transmitted character code to make sure that it has the
selected number (even or odd) of set bits.
The vertical parity bit is positioned immediately following the MSB (Most signifi-
cant bit) as shown below.
(For 7-bit data)
Vertical parity bit
Vertical parity bit
(For 8-bit data)
100000100
LSB MSB
b0 b1 b2 b3 b4 b5 b6
LSB MSB
b0 b1 b2 b3 b4 b5 b6
LSB MSB
b7