DS643 Datasheet, PDF (140/216 Pages) Xilinx, Inc – Soft Direct Memory Access (SDMA) support

LogiCORE IP Multi-Port Memory Controller (v6.06.a)
Receive LocalLink Interface
The LocalLink and Byteshifter Rx logic receives data from the LocalLink interface and moves the data to the
appropriate place in memory. This concept is shown in Figure 23.
In this example:
• The SDMA always ignores the Rx LocalLink Header, which must be only 1 word long.
• The Payload is processed by the Rx Byteshifter and pushed into the MPMC Write FIFOs. The Payload is 270
bytes.
• The data is pushed into the FIFOs in bursts of 32 words (B32W).
• Data is stuffed into the FIFOs from address m through address m+0x7C because the Payload is written to
address m+0x79, which is not a 32-word aligned address.
• When these bytes are written to memory, the byte enables are turned Off.
• In the second B32W, all of the data is valid.
• In the third B32W, only three bytes must be written to memory. This means that the remaining 125 bytes must
be stuffed into the FIFOs at the end of the burst.
• The length of buffer 1 was specified to be 138 bytes long in the Receive descriptor. After the first three bytes,
B32Ws buffer 1 is full.
• The remainder of the payload is transferred to buffer 2.
• The fourth, fifth, and sixth transfers are similar to the first three transfers in that the first valid byte is not at an
even boundary.
• SDMA begins the fourth B32W at r+00, setting the byte enables to Off for all the bytes up to the first valid byte
at r+7E.
• The fifth B32W has all bytes valid, and, in the final B32W, only two bytes are valid.
• The remaining 126 bytes are pushed to the FIFO with the byte enables set to Off.
• After the Payload is processed, the footer is processed and written to memory at address p.
• The SDMA changes the byte enables of the first three words to prevent the Next Descriptor Pointer, Buffer
Address, and Buffer Length values from being overwritten. Thus, only the values of STS_CTRL_APP0, APP1,
APP2, APP3, and APP4 are updated in the memory space.
DS643 February 22, 2013
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Product Specification