ACS ACK30 Smart Keyboard - Manual (Page 15)

ACR30 Reference Manual
Version 3.3 January 2009 Page 15 of 44
ACR30
Data Length Number of subsequent data bytes (0 < N < 255)
Data Data contents of the command.
For a READ_DATA command, for example, the data bytes would contain the contents
of the memory addresses read from the card. The data bytes can represent values
read from the card and/or status information.
Checksum The checksum is computed by XORing all response bytes including header, status
bytes, data length and all data bytes.
The following example shows the structure of the response to a command which has successfully
been executed and which returns three data bytes with the values 11
H
, 22
H
and 33
H
, respectively:
byte 1 2 3 4 5 6 7 8
01
H
90
H
00
H
03
H
11
H
22
H
33
H
92
H
8.2.2. No transmission error with extended response
The response by the ACR30 to a correctly received command consists of three protocol bytes, two
status bytes and a variable number of data bytes and has the following structure:
byte 1 2 3 4 5 6 7 ... N+6
(N>0)
N+7
Header SW1 SW2 Data length = N Data Checksum
FF
H
Data Length
N
Header Always 01
H
to indicate the start of the response.
SW1 Indicates the command execution status:
90
H
= command successfully executed
60
H
= error in command data; command cannot be executed
67
H
= error detected in command execution
FF
H
= status message initiated by the reader
SW2 Further qualification of the command execution status.
A table listing the possible values of the status bytes SW1 and SW2 and the
corresponding meaning is given in Appendix B.
Data Length Number of subsequent data bytes, and is encoded in 3 bytes. The first byte is FF
H
.
The second byte and the third byte represent data length N.
Data Data contents of the command.
For a READ_DATA command, for example, the data bytes would contain the contents
of the memory addresses read from the card. The data bytes can represent values
read from the card and/or status information.