ACS ACK30 Smart Keyboard - Manual (Page 16)

ACR30 Reference Manual
Version 3.3 January 2009 Page 16 of 44
ACR30
Checksum The checksum is computed by XORing all response bytes including header, status
bytes, data length and all data bytes.
8.2.3. Transmission error
If the receiving party of a command (i.e., the ACR30) 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 ACR30 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 ACR30, it can send the 'NOT ACKNOWLEDGE' to the reader upon which
the reader will transmit the most recent response again.
8.3. Reset Message
A reset of the reader occurs automatically whenever the reader is being powered up. A reset can also
be actuated through the RS-232/USB interface. In either case the reader transmits one time a Reset
Message, which has the same structure as the normal response to a command and the following
contents:
byte 1 2 3 4 5 6
Header SW1 SW2 Data length Data Checksum
01
H
FF
H
00
H
01
H
BAUD=12
H
BAUD Indicates the hardware baud rate setting (default baud rate), which is set to 9600 bps
(this is only valid in the RS232 reader).
The reader does not expect an acknowledge signal from the computer. After transmitting the Reset
Message the reader is waiting for the first command from the computer.
8.4. Card Status Message
When a card is being inserted into the reader or an inserted card is being removed from the reader
while the reader is idle, i.e., not executing a command, the reader transmits a Card Status Message to
notify the host computer of the change in the card insertion status.
In a system where these unsolicited messages from the reader to the computer are not desired, they
can be disabled with the SET_NOTIFICATION command. Please note that the setting made with this
command is volatile and will be lost with the next reader reset or power up. By default, the Card
Status Message will be transmitted by the reader after a reset.
The Card Status Messages have the following structure and contents: