Specifications

Operations Manual, Redundant System Controllers 209351 REV B 81
7.3 Access optional SSPA subsystem with Packet Wrapper technique
Features introduced in firmware version 4.03 allow send requests directly to a remote
SSPA subsystem. In this mode, the RCP redirects requests from its Serial Main or
Ethernet port to its Local serial port, connected to the SSPA (see Figure 7-8). Packet
wrapper requests are associated with longer response times, which have to be
accounted in the host M&C software. This mode can be useful for advanced remote
diagnostic of the attached SSPA subsystem.
All Packet Wrapper request frames must be “Data Set” command requests.
Each frame intended for redirection must be included in request packet Data Fields.
Packet Wrapping frame M&C should follow the same rules as for any other request
frames with one exclusion — the Data Address field will represent the number of bytes
expected back from the remote SSPA. These bytes will be redirected back to the Host
M&C in the Data Field response packet. The response packet will not be sent until the
specified number of bytes is collected in the RCP2 buffer.
Maximum length of the data fields in both directions should not exceed 32 bytes.
In the diagram represented in Figure 7-8, Request frame A is the Packet Wrapper
frame. It contains Request frame B, intended to be redirected to the remote SSPA.
Byte Tag Description
1 0xAA Frame Sync 1
2 0x55 Frame Sync 2
3 Destination Address - // -
4 Source Address -// -
5 Protocol Version Protocol Compatibility Byte, must be set 0
6 Request ID Service Byte
7 Command 0 Set Request; 1 Get Request
8 Data Tag
0 System Settings; 1 System Thresholds;
2 Reserved; 3 Conditions; 4 ADC Data;
5 Reserved; 6 Packet Wrapper
9 Data Address
Setting number, Sensor command,
EEPROM address
10 Data Length Total length of the data, valid values: 1 – 10
11+N Data Actual Data
11+N+1 Checksum
Dest. Address + Source Address + Protocol
Version + Request ID + Command + Data Tag +
Data Address + Data Length + Data
Table 7-4: Request Frame Structure