Datasheet

Table Of Contents
If the DW_apb_ssi makes a transmit request to this channel, four data items are written to the DW_apb_ssi transmit FIFO.
Similarly, if the DW_apb_ssi makes a receive request to this channel, four data items are read from the DW_apb_ssi
receive FIFO. Three separate requests must be made to this DMA channel before all 12 data items are written or read.
When the block size programmed into the DMA Controller is not a multiple of the burst transaction length, as shown in
Figure 161, a series of burst transactions followed by single transactions are needed to complete the block transfer.
15 Data Items
15 Data Items
4 Data Items
DMA
Multi-block Transfer
Level
DMA
Block
Level
DMA Burst
Transaction 1
4 Data Items
DMA Burst
Transaction 2
4 Data Items
DMA Burst
Transaction 3
1 Data Items
DMA Single
Transaction 1
1 Data Items
DMA Single
Transaction 2
1 Data Items
DMA Single
Transaction 3
Figure 161.
Breakdown of DMA
Transfer into Single
and Burst
Transactions. Block
size,
DMA.CTLx.BLOCK_
TS = 15. Number of
data iterms per burst
transaction,
DMA.CTLx.DEST_M
SIZE = 4. SSI
transmit FIFO
watermark level,
SSI.DMATDLR =
DMA.CTLx.DEST_M
SIZE = 4
4.11.12. APB Interface
The host processor accesses data, control, and status information on the DW_apb_ssi through the APB interface. APB
accesses to the DW_apb_ssi peripheral are described in the following subsections.
4.11.12.1. Control and Status Register APB Access
Control and status registers within the DW_apb_ssi are byte-addressable. The maximum width of the control or status
register in the DW_apb_ssi is 16 bits. Therefore all read and write operations to the DW_apb_ssi control and status
registers require only one APB access.
4.11.12.2. Data Register APB Access
The data register (DR) within the DW_apb_ssi is 32 bits wide in order to remain consistent with the maximum serial
transfer size (data frame). An APB write operation to DR moves data from pwdata into the transmit FIFO buffer. An APB
read operation from DR moves data from the receive FIFO buffer onto prdata.
The DW_apb_ssi DR can be written/read in one APB access.
NOTE
The DR register in the DW_apb_ssi occupies sixty-four 32-bit locations of the memory map to facilitate AHB burst
transfers. There are no burst transactions on the APB bus itself, but DW_apb_ssi supports the AHB bursts that happen
on the AHB side of the AHB/APB bridge. Writing to any of these address locations has the same effect as pushing the
data from the pwdata bus into the transmit FIFO. Reading from any of these locations has the same effect as popping
data from the receive FIFO onto the prdata bus. The FIFO buffers on the DW_apb_ssi are not addressable.
4.11.12.3. APB 3.0 Support
The register interface of DW_apb_ssi is complaint with APB 3.0 specifications. The pready and pslverr signals are included
to support the APB 3.0 interface. The pready signal is always kept to its default value (HIGH == 1) for all operations except
for XIP operations.
The pslverr signal functionality is disabled.
RP2040 Datasheet
4.11. SSI 619