2. Serial RapidIO Interface > Maintenance Packets
53
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
2.4
Maintenance Packets
Maintenance packets are handled differently than other packets by the Tsi578. In a system the Tsi578
can be the destination of the maintenance packet.
Maintenance packet processing is based on the maintenance packet’s hop count value. The hop count
value controls how many hops the maintenance packet travels before it reaches its destination. The
routing of the maintenance packet is controlled by the destination ID of the packet, the lookup table,
and other values programmed in the intervening devices.
If a maintenance packet has a hop count greater than zero, the Tsi578 decrements the hop count,
recalculates the CRC, and routes the packet out the port selected by the LUT. For this reason, all
maintenance packets must contain routeable source and destination addresses and the routing LUT
must be programmed to route both the maintenance transaction and its response.
If a maintenance read or maintenance write request packet has a hop count of 0, the port processes the
maintenance request and sends a maintenance response packet. The maintenance request is passed to
the register bus as a read or write transaction, an address offset, and any data associated with the
request. The maintenance response packet is generated by the Tsi578 using the success or failure of the
access and data from a read operation. CRC is computed and the packet is enqueued for transmission
on the port that received the maintenance request.
Each port can have only one outstanding maintenance request at a time. A maintenance request
received while another maintenance is being processed is retried by the RapidIO port.
The Tsi578 supports 4 byte maintenance requests only. With hop count equals 0, any Maintenance
Requests larger than 4 bytes, as well as maintenance packets that are not read or write requests, are
dropped and an error is noted in the IMP_SPEC_ERR bit in the
“RapidIO Port x Error Detect CSR” on
. Examples of maintenance packets that are dropped are maintenance response and port-write
packets received with a hop count of 0.
Ensure the destination IDs of the maintenance packet does not match the destination ID of a
multicast packet. If there is a match, system behavior is undefined.
Table 3: Examples of Maintenance Packets with Hop Count = 0 and Associated Tsi578 Responses
Transaction Type
Size Field
Action taken by
Tsi578
Error Logging
Notes
Read or Write
Request
4 bytes
Response generated
with status ok
N/A
Accepted address space = 00000 to
1FFFF
4 bytes
Send Maintenance
Response with Status
Error (0111)
N/A
Address space specified > 1FFFF
4 bytes
Send Maintenance
Response with Status
Error (0111)
N/A
Not supported by Tsi578