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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 367
UG585 (v1.11) September 27, 2016
Chapter 13: SD/SDIO Controller
In DMA mode, the host controller initiates a DMA READ from the ARM processor only if space is
available to accept a block of data.
In non-DMA mode, the host controller asserts a buffer write ready interrupt only if space is
available to accept a block of data.
Read
During the read transaction when the FIFO is full (the FIFO does not have enough space to accept a
block of data from the card) the host controller stops the clk_sd to the card. Therefore an over-run
condition cannot occur in SD side.
In DMA mode the host controller initiates a DMA WRITE to the ARM processor only on
reception of a block of data from card.
In non-DMA mode, the host controller asserts a buffer read ready interrupt only on reception of
a block of data from card.
13.3 Programming Model
13.3.1 Data Transfer Protocol Overview
SD transfers are basically classified into following three types according to how the number of blocks
is specified:
Single Block Transfer
The number of blocks is specified to the host controller before the transfer. The number of blocks
specified is always one.
Multiple Block Transfer
The number of blocks is specified to the host controller before the transfer. The number of blocks
specified is one or more.
Infinite Block Transfer
The number of blocks is not specified to the host controller before the transfer. This transfer is
continued until an abort transaction is executed. This abort transaction is performed by CMD12 in
the case of an SD memory card and by CMD52 in the case of an SDIO card.
13.3.2 Data Transfers Without DMA
Figure 13-3 shows data transfers without using DMA.