eCPRI Intel® FPGA IP User Guide

ID 683685
Date 2/22/2024
Public
Document Table of Contents

4.3.8.5. eCPRI Message Type 4- Remote Memory Access

Table 23.  eCPRI Message Type 4- Remote Memory Access Message Format
0 (MSB) 1 2 3 4 5 6 7 (LSB) No. of Bytes
Remote Memory Access ID 1
Read/Write Req/Resp 1
Element ID 2
Address 6
Length 2
Data L

The eCPRI IP core supports two different modes for remote memory access message type: basic mode and buffer mode. The basic mode provides direct tunneling on the memory access, with all the necessary information for the memory access output to user logic. User logic is responsible to send the same ID/Element ID upon responding to the original request.

The buffer mode keeps the receiving request ID/Element ID/Address/read/write operations per table below. User logic carries out the operation and response to the original request with number of read/write bytes and read data. eCPRI IP appends necessary fields and then send the eCPRI message back to sender.

eCPRI IP expects the request and response to be in-order for this buffer mode. eCPRI IP can hold up to a maximum of eight pending requests. If there are eight pending requests in the queue and there is additional request received, the IP drops the additional request and logs error in RX error register.

eCPRI IP operates in basic mode by default.
Table 24.  Parameter Handling
Action ID Read/Write Request/Response Element ID Address Length Data
Read request Set Set to read Set to request Set Set Set No data
Read response Copied Copied Set to response Copied Copied No. of read bytes Read data
Write request Set Set to write Set to request Set Set Set The data to be written
Write response Copied Copied Set to response Copied Copied No. of written bytes Vendor specific
Write no response Set Set to write no response Set to request Set Set Set The data to be written
Failure response Copied Copied Set to Failure Copied Copied Vendor specific Vendor specific
Figure 16. eCPRI Message Type 4 – Remote Memory Access in Basic Mode Message Timing Diagram

The waveform below illustrates the buffer mode where read request is sent to user logic. User logic response with read data and the actual length of the operation and message type 4. eCPRI IP extracts the memory access ID/element ID and address from internal buffer and combine with read data to send back to sender.

Figure 17. eCPRI Message Type 4 – Remote Memory Access Message in Buffer Mode Timing Diagram