LSI Logic Confidential
SIO SPI (Serial Peripheral Interface)
15-11
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
may be either the MSB or the LSB of the value written into
SPI_TEMP.
3.
Inter-Byte Spacing: SIO_SPI_CLK is gated in-between bytes. The
amount of time between successive bytes transferred can be
adjusted by programming the CSDL and IBBK fields in the
SPI_CONFIG register. Depending on the value of CSBK,
SIO_SPI_CS may or may not be asserted during this inter-byte
spacing time.
4.
Last Bit of Data Transfer: The final bit of the value written into
SPI_TEMP is shifted out the SIO_SPI_MOSI pin and is shifted in the
SIO_SPI_MISO pin. This may be either the MSB or the LSB,
depending on the value of LSBF in the SPI_CONFIG register.
5.
SIO_SPI_CS de-asserts: Chip select signal deasserts, data transfer
is terminated. The CSDL field again determines the number of 1/2
SIO_SPI_CLK cycles between SIO_SPI_CS negation and
SIO_SPI_CLK gating.
15.2.3 SPI Clocking
The SPI module is synchronous to the system clock (sysclk), and all
flops in the module are clocked by this system clock. The module uses
an internal Clock Enable to generate SIO_SPI_CLK. This enable is
programmable by the host, and is used to set the SIO_SPI_CLK
frequency at one half the Clock Enable rate.
The SPI module can support a SIO_SPI_CLK rate from 4.58 kHz to 37.5
MHz. Note that most SPI slave devices ignore gaps of time between
active bytes on the interface, with the bus operations being paced by
active edges of the SIO_SPI_CLK.
The programmable value for SIO_SPI_CLK is given by the following
equation:
where progdiv is the value written to the programmable divider
(HDIV,SPED).
f
spiclk
f
sysclk
2
progdiv
2
+
(
)
×
----------------------------------------------
=
Содержание DMN-8600
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