Symbol SE 923, Integration Manual

Page: 167 / 238

6-11
Simple Serial Interface
CMD_ACK
Description: Positive acknowledgment of received packet
Packet Format
Field Descriptions
This message is sent to the SSI packet transmitter when the received packet passes the
checksum check and no negative acknowledgment conditions apply (see CMD_NAK). If the
data is in response to a command (e.g., PARAM_REQUEST, REQUEST_REVISION, etc.),
no ACK is sent.
Note: ACK/NAK handshaking can be disabled. We recommend, however, it
be left enabled.
It is not necessary to respond to a valid ACK or NAK message.
Length Opcode Message Source Status Data Checksum
0x04 0xD0
Field Name Format Size Description
Length Length of message (not
including checksum). 1 Byte Length Field
Opcode 0xD0 1 Byte Identifies this Opcode type.
Message
Source 0 = Decoder
4 = Host 1 Byte Identifies where the message is
coming from.
Status Bit 0: Retransmit
Bit 1-7: unused 1 Byte Identifies the transmission status.
All unused bits must be set to 0.
Data None
Checksum 2's complement sum of
message contents
excluding checksum. 2 Bytes Checksum of message.