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4.2.2 Error Checking
4.2.2.1 ACK/NAK
When the camera receives a frame, it checks the order of the bytes in the frame and checks to
see if the XOR sum of the bytes in the descriptor and the data fields matches the block check
character. The camera also checks to see if the number of bytes in the data field is equal to the
number specified in the descriptor.
If all checks are correct, an ACK is send to the host. If any check is incorrect, a NAK is sent.
4.2.2.2 Time-outs
Byte Time-out
The camera checks the time between the receipt of each byte in the frame. If the time between
any two bytes exceeds 1 second, the camera enters a "garbage state" and discards any more
incoming bytes. The camera remains in this state until it sees 1.5 seconds of silence. Once the
camera sees 1.5 seconds of silence, it goes into an idle state (looking for an STX).
4.2.2.3 Read Command
In the normal case, when a read command is sent to the camera, the camera responds with an
ACK and a frame. The frame will contain the data requested in the read command.
If the camera receives a read command with an unknown command ID in the descriptor, it will
respond with an ACK but will not send a frame.
If the host sends a read command and gets no ACK/NAK, the host can assume that no camera is
present.
If the host sends a read command and gets an ACK/NAK but does not receive a frame within 500
ms, the host can assume that there was a problem with the read command.
4.2.2.4 Write Command
In the normal case, when a write command is sent to the camera, the camera responds with an
ACK.
If the camera receives a write command with an unknown command ID in the descriptor, it will
respond with an ACK but will not perform the write.
After a write command has been issued by the host, the host can verify the write by issuing a
corresponding read command and checking that the returned data is as expected. The host can
also issue a camera status read command (see Section 4.2.7) and check the returned data to see
if an error condition has been detected.
For many of the write commands listed in the tables on pages 4-10 through 4-28,
only data within a specified range or a specified group of values is valid. The camera
does not perform a check to see if the data in the write command is within the al-
lowed range or specified group of allowed values.
k
BASLER A102
DRAFT
Configuring the Camera
4-7
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