Figure 1. Write Transactions
A summary of component behavior during a typical write transaction is as follows:
- The AXI master sends a write request to the NMU.
- The NMU performs the following functions:
- Asynchronous crossing and rate-matching from the PL master clock domain to the NoC clock domain.
- Destination lookup of the target NSU.
- Address remapping (in cases of virtualization).
- AXI conversion of the write request (
AxAddr
,AxSize
,AxLen
,AxBurst
,AxCache
,writestrobe
, andwritedata
) from theAxSizeMaster
to theAxSizeNoC
. - Write chopping.
- Single-slave-per-id (SSID) check for outstanding write transactions with the same AXI-ID but with a different DST (NoC destination ID).
- Write tracker entry insertion.
- Packetizing of the write request into the NPP packet format, rate limiting, and ECC generation.
- VC-mapping and VC-arbitration before sending the packet to the NoC channel.
- The NMU forwards the NPP to an NPS in the system.
- The NPS performs the same steps as for a read operation.
- Destination table lookup for the target out port.
- Least Recently Used (LRU) arbitration at the output port (24:1).
- The NPP write packets are (possibly) passed through multiple NPSs before they reach the destination NSU.
- At the destination, the NSU performs the following functions:
- De-packetizing of the write request and ECC checking and correction.
- Write chopping for downsizing.
- Write tracker entry insertion.
- AXI conversion of the request from the
AxSizeNoC
to theAxSizeSlave
. - Asynchronous crossing and rate-matching from the NoC clock domain to the PL slave clock domain.
- Sending the AXI format write request to the NoC AXI slave.
- The write request is processed by the slave AXI, which returns the response to the NSU.
- The NSU performs the following functions:
- Asynchronous crossing and rate-matching from the PL slave clock domain to
the NoC clock domain.
- Merges the write responses in write tracker (in cases of write chopping).
- Packetizes the write response into NPP packets and generates ECC.
- VC-mapping, VC-arbitration before sending the packet to the NoC channel.
- Asynchronous crossing and rate-matching from the PL slave clock domain to
the NoC clock domain.
- The NPP formatted write response packets pass through a single NPS or multiple NPSs before reaching the NMU.
- When the write response packets reach the NMU, it performs the following
functions:
- ECC checking, ECC correction and de-packetizing of the write response.
- Merges the write responses (in cases where write chopping is performed during write requests).
- Asynchronous crossing and rate-matching from the NoC clock domain to the PL master clock domain.
- Returns the write response back to the NoC AXI master.
- ECC checking, ECC correction and de-packetizing of the write response.