User's Manual

18
Micro-reader - Reference Guide May ’00
2.1.5 BCC
The 'BCC' field is a one-byte value of the Longitudinal Redundancy Check calcula-
tion (Xor'ed bytes) for the preceding message. The calculation is performed on the
whole message excluding the Start-Mark.
Example:
02 08 32
02 0000 0010
08 0000 1000
--------------------------------
XOR 0000 1010
32 0011 0010
--------------------------------
XOR 0011 1000 = 38 (hex)
2.2 Protocol Micro-reader to PC
Byte Contents (hexadecimal value)
0 Start Mark (SOH, 01
hex
)
1 Length
2Status
3 Data Field (1) (LSByte)
.
.
.
N+2 Data Field (N) (MSByte)
N+3 BCC
Refer to section 5.2 for examples.
2.2.1 Start Mark
The 'Start-Mark' signifies the beginning of a message. It is represented by the ASCII
character SOH (Start Of Header: 01
hex
)
2.2.2 Length
The 'Length' byte indicates the length, in bytes, of the following Status and Data
Fields.
Start
Length
BCCStatus Data