User's Manual

15
May ’00 Chapter 2. Communications Protocol
2.1 Protocol PC to Micro-reader
Byte Contents (hexadecimal value)
0 Start Mark (SOH, 01
hex
)
1 Length
2 Command Field (1)
3 Command Field (2) (optional)
4(3) Data Field (1)
.
.
N+3(2) Data Field (N)
N+4(3) BCC
Examples are given in section 5.1.
2.1.1 Start Mark
The 'Start-Mark' signifies the beginning of a message. It is represented by the ASCII
character SOH (Start Of Header, 01
hex
).
2.1.2 Length
The 'Length' byte indicates the length, in bytes, of the following Command and Data
Fields.
Note:
The total number of bytes sent within a protocol frame (including Start
Mark and BCC) is limited to 41 bytes.
Start Length
BCC
Cmd 1 Cmd 2 Data