Ameba-D User Manual
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Fig 19-5 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. Fig 19-6 shows the timing diagram for continuous SPI
transfers when the configuration parameter SCPH = 1.
Fig 19-6 SPI Serial Format Continuous Transfers (SCPH = 1)
19.2.1.2
Clock Ratios
When SPI is configured as a master device, the maximum frequency of the bit-rate clock (sclk_out) is one-half the frequency of ssi_clk. This
allows the shift control logic to capture data on one clock edge of sclk_out and propagate data on the opposite edge; this is illustrated in Fig
19-7. The sclk_out line toggles only when an active transfer is in progress. At all other times it is held in an inactive state, as defined by the
serial protocol under which it operates.
The frequency of sclk_out can be derived from the following equation:
𝐹
𝑠𝑐𝑙𝑘_𝑜𝑢𝑡
=
𝐹
𝑠𝑠𝑖_𝑐𝑙𝑘
SCKDV
SCKDV is a bit field in the programmable register BAUDR, holding any even value in the range 0 to 65,534. If SCKDV is 0, then sclk_out is
disabled.
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2019-05-15 10:08:03