Arria V Avalon-ST Interface for PCIe Solutions User Guide

ID 683733
Date 6/03/2020

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4.11. LMI Signals

LMI interface is used to write log error descriptor information in the TLP header log registers. The LMI access to other registers is intended for debugging, not normal operation.

Figure 40. Local Management Interface

The LMI interface is synchronized to pld_clk and runs at frequencies up to 250 MHz. The LMI address is the same as the Configuration Space address. The read and write data are always 32 bits. The LMI interface provides the same access to Configuration Space registers as Configuration TLP requests. Register bits have the same attributes, (read only, read/write, and so on) for accesses from the LMI interface and from Configuration TLP requests.

Note: You can also use the Configuration Space signals to read Configuration Space registers. For more information, refer to Transaction Layer Configuration Space Signals.

When a LMI write has a timing conflict with configuration TLP access, the configuration TLP accesses have higher priority. LMI writes are held and executed when configuration TLP accesses are no longer pending. An acknowledge signal is sent back to the Application Layer when the execution is complete.

All LMI reads are also held and executed when no configuration TLP requests are pending. The LMI interface supports two operations: local read and local write. The timing for these operations complies with the Avalon-MM protocol described in the Avalon Interface Specifications. LMI reads can be issued at any time to obtain the contents of any Configuration Space register. LMI write operations are not recommended for use during normal operation. The Configuration Space registers are written by requests received from the PCI Express link and there may be unintended consequences of conflicting updates from the link and the LMI interface. LMI Write operations are provided for AER header logging, and debugging purposes only.

  • In Root Port mode, do not access the Configuration Space using TLPs and the LMI bus simultaneously.
Table 38.  LMI Interface






Data outputs.



Read enable input.



Write enable input.



Write execution done/read data valid.



Address inputs, [1:0] not used.



Data inputs.

Figure 41. LMI Read
Figure 42. LMI Write Only writable configuration bits are overwritten by this operation. Read-only bits are not affected. LMI write operations are not recommended for use during normal operation with the exception of AER header logging.