3 ] Crc; 4 ] Id - Denso BHT-100B User Manual

[ 3 ] CRC

To check whether data has been transmitted accurately, the BHT-Ir protocol supports
CRC (Cyclic Redundancy Check) which employs the CRC-16 generating system. In
CRC, a CRC character is suffixed to a sequence of DLE ETX of every transmission block.
Operands for CRC-16
The CRC generates CRC-16 from all bytes of a transmission block excluding DLE SOH
or DLE STX characters (which are at the head of a transmission block), DLE character
of DLE ETX and DLE character of DLE DLE in the text.
CRC operation
The CRC system generates CRC-16 as follows: It multiplies the polynomial formed by
aligning all of the bits starting from the LSB of the first byte to the MSB of the last byte
in a transmission block in descending order, by X
the generative polynomial X
Shown below is a data text transmission block and operands for CRC-16 generation.
D S
• T
L
E X

[ 4 ] ID

ID is a 2-digit hexadecimal and designated in 0000h through FFFFh in (2 bytes). 0000h
is assigned to the host computer. Any of 0001h through FFFFh is assigned to the BHT
as follows.
• The system sets an ID when the BHT is initialized.
• You may set an arbitrary ID in System Mode or by using the OUT statement in
BHT-BASIC.
16 15 2
+ X + X + 1. The remainder is the value of CRC-16.
I
Serial
Data text
number
D
Operands
183
16
. Next, divide the polynomial by
D E C
T R
L •
E X C
Operand
Appendices