User's Manual

PC-Card Transponder Reader – Release 1.0
HERMOS Informatik GmbH, 95490 Mistelgau, Germany
Page 14 of 17
2002-09-04
ID: ID020064
7 Protocol
7.1 Message Structure
All messages have the following structure:
Length Header Data Chksum
1 byte 2 bytes 1 or more bytes 2 bytes
Header
Command Action #
Length: Number of bytes of Header and Data
(without Length and Chksum).
Header: Consists of Command and Action #
Command: Defines the function of the message.
Action #: To distinguish the single messages the Action # will be increased
for each new message.
Data: The content depends of the message type.
ChkSum: 2 bytes checksum over Length, Header and Data (sum of byte
values).