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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
636 of 1441
NXP Semiconductors
UM10503
Chapter 24: LPC43xx/LPC43Sxx SPI Flash Interface (SPIFI)
The SPI protocol avoids all issues of set-up and hold times between the clock and data
lines by using half of the SCK period to transmit the data. For high clock speeds, it is
necessary to sample read data using a feedback clock. The FBCLK bit enables the
feedback clock from the SCK pad sampling method. This provides the best possible
timing margin for both read and write data under the opposite-edge scheme.
But maximizing clock frequency is of such importance that further improvement is
sometimes needed, by means of using the whole serial clock period to transmit data. This
choice is enabled for read data by setting the RFCLK bit. When this bit is 1, the SPIFI
samples data on the falling edge of the serial clock that follows the rising edge which is
normally used. RFCLK and FBCLK and MODE3 should not all be 1 because in this case
there would be no falling edge of the feedback clock to capture the last bit of a frame.
Consult the datasheet of the serial flash device to be used for the formats of the
commands that it supports.
shows commands consisting of an opcode field
only, sent in SPI and quad modes. All fields are multiples of 8 bits long. Bytes are sent
with the most significant bit first in SPI mode, and the most significant 4 bits first in quad
mode.
shows a command that reads 1 byte from the slave in SPI mode and a
command that reads 3 bytes from the slave with the opcode and input data fields both in
quad mode.
Opcode-only command in SPI mode
Opcode-only command in quad mode
Fig 64. Opcode only commands
SPIFI_SCK
SPIFI_CS
SPIFI_MOSI
SPIFI_SCK
SPIFI_CS
IO0 (SPIFI_IO0)
IO1 (SPIFI_IO1)
IO2 (SPIFI_SIO2)
IO3 (SPIFI_SIO3)