Datasheet

Table Of Contents
Figure 122 shows the timing diagram for the SPI format when the configuration parameter SCPH = 1.
sclk_out/in 0
sclk_out/in 1
txd
rxd
ss_0_n/ss_in_n
ssi_oe_n
MSB
4 -32 bits
LSB
MSB LSB
Figure 122. SPI Serial
Format (SCPH = 1)
Continuous data frames are transferred in the same way as single frames, with the MSB of the next frame following
directly after the LSB of the current frame. The slave select signal is held active for the duration of the transfer.
Figure 123 shows the timing diagram for continuous SPI transfers when the configuration parameter SCPH = 1.
sclk_out/in 0
sclk_out/in 1
txd
rxd
ss_0_n/ss_in_n
ssi_oe_n
MSB LSB LSBMSB
MSB LSB LSBMSB
Figure 123. SPI Serial
Format Continuous
Transfer (SCPH = 1)
There are four possible transfer modes on the DW_apb_ssi for performing SPI serial transactions. For transmit and
receive transfers (transfer mode field (9:8) of the Control Register 0 = 00b), data transmitted from the DW_apb_ssi to the
external serial device is written into the transmit FIFO. Data received from the external serial device into the DW_apb_ssi is
pushed into the receive FIFO.
Figure 124 shows the FIFO levels prior to the beginning of a serial transfer and the FIFO levels on completion of the
transfer. In this example, two data words are transmitted from the DW_apb_ssi to the external serial device in a
continuous transfer. The external serial device also responds with two data words for the DW_apb_ssi.
Tx FIFO Buffer
FIFO Status Prior to
Transfer
FIFO Status on
Completion of Transfer
Rx FIFO Buffer
Location n
Location 2
Location 1
Location 0
Location n
Location 2
Location 1
Location 0
Write DR
NULL
NULL SHIFT LOGIC
Tx Data(1)
Tx Data(0)
Rx FIFO Empty
rxd
txd
NULL
Rx_Data(1)
Rx_Data(0)
NULL
Tx FIFO Empty
Read DR
Figure 124. FIFO
Status for Transmit &
Receive SPI and SSP
Transfers
For transmit only transfers (transfer mode field (9:8) of the Control Register 0 = 01b), data transmitted from the
DW_apb_ssi to the external serial device is written into the transmit FIFO. As the data received from the external serial
device is deemed invalid, it is not stored in the DW_apb_ssi receive FIFO.
Figure 125 shows the FIFO levels prior to the beginning of a serial transfer and the FIFO levels on completion of the
transfer. In this example, two data words are transmitted from the DW_apb_ssi to the external serial device in a
continuous transfer.
RP2040 Datasheet
4.11. SSI 603