75
4-2 CMD_ACK
Description: Positive acknowledgment of received packet.
Packet Format
Length
Opcode
Status
Checksum
0x03
0x59
(‘Y’)
Field Descriptions
Table 4-3 Field Descriptions
Field name
Format
Size
Description
Length
Length of message (not
including checksum).
1 byte
Length of Field
Opcode
0x59
1 byte
Identifies the command opcode type.
Status
Bit 0：Retransmit
Bit 1-6：unused
Bit 7: Command source
1 byte
Bit 0: Identifies the transmission status.
Bit 7：
1, Command is from the host.
0, Command is from the scanner.
All unused bits must be set to 0.
Checksum
2’s complement sum of
message contents excluding
checksum
2 bytes
Checksum of message
CMD_ACK message is sent to the UART packet transmitter when the received packet passes the
checksum check and no negative acknowledgment conditions apply. If the data to be sent is in response
to a command (e.g. REQUEST_REVISION), CMD_ACK message is not in need.
When ACK/NAK handshaking is disabled, the CMD_ACK message will not be sent.
It is not necessary to respond to a valid ACK or NAK message.
For example:
Length
Opcode Status Checksum
0x03
0x59
0x00
0xFF 0XA4
Host Requirements
The host must send a CMD_ACK or response data within the programmable Host Serial Response
Time-out to acknowledge receipt of all messages, unless noted otherwise in the message description
section. If the host sends data and does not receive a response within the programmable Host Serial
Response Time-out, it resends the message (with the retransmit status bit set) before declaring a failure.
The host should limit the number of retries.
Scanner Requirements
The scanner must send a CMD_ACK or response data within the programmable Host Serial Response
Time-out to acknowledge receipt of all messages, unless noted otherwise in the message description
