ACS AET65 Smart Card Reader with Fingerprint Sensor - Manual (Page 11)

8.0. Communication Protocol
8.1. AET65 Communication Protocol
During normal operation, the AET65 acts as a slave device with regard to the communication between
a computer and the reader. The communication is carried out in the form of successive command-
response exchanges. The computer transmits a command to the reader and receives a response
from the reader after the command has been executed. A new command can be transmitted to the
AET65 only after the response to the previous command has been received.
There are two cases where the reader transmits data without having received a command from the
computer namely, the Reset Message and the Card Status Message.
8.1.1. Command to AET65
A command consists of six protocol bytes and a variable number of data bytes with the following
structure:
Byte 1 2 3 4 5 ... N+4 (N>0)
Header Instruction Data Length = N Data
01H
Data
Length N
Header Always 01H to indicate the start of a command.
Instruction The instruction code of the command to be carried out by the AET65.
Data Length Number of subsequent data bytes, and is encoded in 2 bytes. The first byte
(MSB) and second byte (LSB) represent data length N.
Data Data contents of the command.
For a READ command, for example, the data bytes would specify the start
address and the number of bytes to be read. For a WRITE command, the
data bytes would specify the start address and the data to be written to the
card.
The data bytes can represent values to be written to a card and/or command
parameters such as an address, a counter, etc.
Note: Commands are sent from host computer to AET65 through the BULK OUT endpoint.
8.1.2. Response from AET65
The response from the AET65 to any command depends on whether the command has been
received by the reader without error (e.g., checksum error).
The response by the AET65 to a correctly received command consists of three protocol bytes, two
status bytes and a variable number of data bytes with the following structure:
Byte 1 2 3 4 5 ... N+4 (N>0)
Header Status Data Length = N Data
01H
Data Length
N
Header Always 01H to indicate the start of the response.
Status Indicates the command execution status:
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AET65 Reference Manual
Version 1.00
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