Write Transactions - 1.0 English

Versal ACAP Programmable Network on Chip and Integrated Memory Controller LogiCORE IP Product Guide (PG313)

Document ID
PG313
Release Date
2022-12-14
Version
1.0 English
Figure 1. Write Transactions

A summary of component behavior during a typical write transaction is as follows:

  1. The AXI master sends a write request to the NMU.
  2. 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, and writedata) from the AxSizeMaster to the AxSizeNoC.
    • 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, VC-arbitration, and DBI generation before sending the packet to the NoC channel.
  3. The NMU forwards the NPP to an NPS in the system.
  4. 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).
  5. The NPP write packets are (possibly) passed through multiple NPSs before they reach the destination NSU.
  6. 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 the AxSizeSlave.
    • 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.
  7. The write request is processed by the slave AXI, which returns the response to the NSU.
  8. 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.
  9. The NPP formatted write response packets pass through a single NPS or multiple NPSs before reaching the NMU.
  10. When the write response packets reach the NMU, it performs the following functions:
    • DBI and 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.