1.1
Identification (1 byte hexadecimal)
Specific for each command (see table following pages).
1.2
Length (2 bytes in hexadecimal)
The length is the number of bytes comprised between the length and the checksum byte.
1.3
Data
Zero byte in case of request from the calculator to the printer.
1 byte precised the jet number in case of a request concerning a jet.
n bytes following one byte precising the jet number in case of a sent concerning a jet.
n bytes without precising the jet number in case of a sent concerning the printer in general.
1.4
Control byte (Checksum)
This represents an "OR" exclusive of all preceding bytes (identification, length and data bytes).
Table of the "exclusive OR" Boolean function used for the checksum
X
Y
Result
0
0
0
0
1
1
1
0
1
1
1
0
Example of checksum calculation for two bytes:
– Value: 15h in binary
00010101
– Value: 56 h in binary
01010110
Result
01000011
Or, in hexadecimal = 43 h
General principle of a V24 exchange
A13862 Version E
Page 3-3
