1. SM20 Integration Guide
  2. SSI Interface
  3. Encapsulation of RSM Commands/Responses over SSI
  • SM20 Integration Guide
Encapsulation of RSM Commands/Responses over SSI

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 scanner does not support this. The host must fragment packets using the provisions in the RSM protocol.

Command Structure

Byte
7
6
5
4
3
2
1
0
0
Length (not including the checksum)
1
SSI_MGMT_COMMAND (0x80)
2
Message Source (4 - Host)
3
Reserved (0)
Reserved (0)
Reserved (0)
Cont'd packet
Retransmit
4
Payload data (see the following example)
...
Length -1
Length
2's complement checksum (MSB)
Length +1
2's complement checksum (LSB)
The expected positive response is SSI_MGMT_COMMAND which can be a multi-packet response. Devices that do not support this command respond with the standard SSI_NAK.

Response Structure

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