ACS AET63 BioTRUSTKey - Manual (Page 12)

NOTE: If the card is being removed from the reader while a card command is being executed, the
reader will transmit a normal response to the computer with the response status bytes indicating the
card removal during command execution (see Appendix B: Response Status Codes).
6.4. Transmission Protocol
The start of a command (to the reader) or a response (from the reader, including the Reset Message
and Card Status Messages) is indicated by the respective party through the transmission of the single
byte Start-of-Text (STX) character with the value 02
H
.
The end of a command or response is indicated through the single byte End-of-Text (ETX) character
with the value 03
H
.
Within the command and response transmission only ASCII characters representing the hexadecimal
(hex) digits 0...F are used. Each byte of a command or response is split into its upper and lower
halfbyte (nibble). For each halfbyte is transmitted the ASCII character representing the respective hex
digit value. For example, to transmit the data byte 3A
H
, two bytes are actually sent on the interface,
namely, 33
H
(ASCII code for '3') followed by 41
H
(ASCII code for 'A'):
Data byte value 3A
H
Transmitted values 33
H
= '3' 41
H
= 'A'
The following example shows the transmission of a command with instruction code A2
H
and one data
byte with the value 3D
H
. The command has the following structure:
Byte 1 2 3 4 5
Header Instructio
n
Data
length
Data Checksum
01
H
A2
H
01
H
3D
H
9F
H
This command is transmitted on the serial interface in 12 bytes as follows:
Byte 1 2 3 4 5 6 7 8 9 10 11 12
STX '0' '1' 'A' '2' '0' '1' '3' 'D' '9' 'F' ETX
02
H
30
H
31
H
41
H
32
H
30
H
31
H
33
H
44
H
39
H
46
H
03
H
For the representation of the hex halfbyte values as the corresponding ASCII characters in
commands, the AET63 accepts both upper case characters 'A' ... 'F' (41
H
... 46
H
) and lower case
characters 'a' ... 'f' (61
H
... 66
H
):
Byte 1 2 3 4 5 6 7 8 9 10 11 12
STX '0' '1' 'A' '2' '0' '1' '3' 'D' '9' 'F' ETX
02
H
30
H
31
H
41
H
32
H
30
H
31
H
33
H
44
H
39
H
46
H
03
H
... is equivalent to:
Byte 1 2 3 4 5 6 7 8 9 10 11 12
STX '0' '1' 'a' '2' '0' '1' '3' 'd' '9' 'f' ETX
02
H
30
H
31
H
61
H
32
H
30
H
31
H
33
H
64
H
39
H
66
H
03
H
In its response messages, the AET63 uses upper case characters 'A' ... 'F'.
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Document Title Here AET63 Reference Manual
Version 2.2
Page 12 of 26
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