ACS AET60 BioCARDKey, Reference Manual

Page: 12 / 24

6.2.2. No Transmission Error with Extended Response
The response by the BioCARDKey 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.
Checksum The checksum is computed by XORing all response bytes including header, status th
and all data bytes.
6.2.3. Transmission Error
If the receiving party of a command (i.e., the BioCARDKey) or a response (i.e., the computer) detects
an error in the data length or the checksum of a command, it disregards the received data and sends
a "NOT ACKNOWLEDGE" message to the transmitting party upon completion of the faulty
transmission. The "NOT ACKNOWLEDGE" message consists of two bytes:
byte 1 2
05
H
05
H
If the BioCARDKey responds with a 'NOT ACKNOWLEDGE' message to a command from the
computer, the computer would normally transmit the command again.
If the computer detects a transmission error in a response from the BioCARDKey, it can send the
'NOT ACKNOWLEDGE' to the reader upon which the reader will transmit the most recent response
again.
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AET60 Reference Manual
Version 1.7
Page 12 of 24
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