Encapsulation Of Rsm Commands/Responses Over Ssi; Command Structure; Response Structure - Symbol DS4308 Product Reference Manual

7 - 8 DS4308/DS4308P Digital Scanner Product Reference Guide

Encapsulation of RSM Commands/Responses over SSI

The SSI protocol allows the host to send a command that is variable in length up to 255 bytes. Although there
is a provision in the protocol to multi-packet commands from the host, the scan engine does not support this.
The host must fragment packets using the provisions in the RSM protocol.

Command Structure

Byte 7
0 Length (not including the checksum)
1 SSI_MGMT_COMMAND (0x80)
2 Message Source (4 - Host)
3 Reserved (0)
4 Payload data (see the following example)
...
Length -1
Length 2's complement checksum (MSB)
Length +1 2's complement checksum (LSB)
The expected response in the positive case is SSI_MGMT_COMMAND which may be a multi-packet
response. For devices that do not support the SSI_MGMT_COMMAND, the response is the standard
SSI_NAK.

Response Structure

Byte 7
0 Length (not including the checksum)
1 SSI_MGMT_COMMAND (0x80)
2 Message Source (0 - Decoder)
3 Reserved (0)
4 Payload data (see the following example)
...
Length -1
Length 2's complement checksum (MSB)
Length +1 2's complement checksum (LSB)
6 5 4
Reserved (0)
6 5 4
Reserved (0)
3 2
Reserved (0)
3 2
Reserved (0)
1 0
Cont'd packet Retransmit
1 0
Cont'd packet Retransmit