18.104.22.168. eCPRI Message Type 4- Remote Memory Access
|0 (MSB)||1||2||3||4||5||6||7 (LSB)||No. of Bytes|
|Remote Memory Access ID||1|
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.
|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|
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.