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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
635 of 1441
NXP Semiconductors
UM10503
Chapter 24: LPC43xx/LPC43Sxx SPI Flash Interface (SPIFI)
24.6.8 SPIFI status register
This register indicates the state of the SPIFI.
24.7 Functional description
24.7.1 Data transfer
Serial SPI uses the signals SPIFI_SCK, SPIFI_CS,SPIFI_MISO, and SPIFI_MISO, while
quad mode adds the two IO signals SPIFI_SIO[3:2].
The SPIFI implements basic, dual, and quad SPI in half-duplex mode, in which the SPIFI
always sends a command to a serial flash memory at the start of each frame. (A frame is
the sequence of bytes transmitted during one period with CS LOW.) In general,
commands start with an opcode byte although some serial flashes allow a no-opcode
mode in which commands start with the address to be read. In write commands, the SPIFI
sends all of the data in the frame, while in read commands, the SPIFI sends the
command, and then the serial flash sends data to the SPIFI.
Classic SPI includes four modes (mode 0 to mode 3), of which the SPIFI and most serial
flashes implement modes 0 and 3. In mode 0, the SCK line is LOW between frames while
in mode 3 it is HIGH. In mode 0, the SPIFI drives the first data bits from the time that it
drives CS LOW, and drives the rest of the data on falling edges of SCK. In mode 3, the
SPIFI drives SCK LOW one-half clock period after it drives CS LOW, and drives data on
the falling edge of SCK. In either mode the serial flash samples the data on the rising
edges of SCK.
The same scheme (transmitter changes data on falling edges of SCK, receiver samples
data on rising edges) is maintained for the entire frame, including read data sent by the
serial flash to the SPIFI.
Table 455. SPIFI status register (STAT, address 0x4000 301C) bit description
Bit
Symbol
Description
Reset
value
0
MCINIT
This bit is set when software successfully writes the Memory
Command register, and is cleared by Reset or by writing a 1 to the
RESET bit in this register.
0
1
CMD
This bit is 1 when the Command register is written. It is cleared by
a hardware reset, a write to the RESET bit in this register, or the
deassertion of CS which indicates that the command has
completed communication with the SPI Flash.
0
3:2
Reserved
0
4
RESET
Write a 1 to this bit to abort a current command or memory mode.
This bit is cleared when the hardware is ready for a new
command to be written to the Command register.
5
INTRQ
This bit reflects the SPIFI interrupt request. Write a 1 to this bit to
clear it. This bit is set when a CMD was previously 1 and has been
cleared due to the deassertion of CS.
5
23:6
-
Reserved
0
31:24
VERSION
The SPIFI hardware described in this chapter returns
0x02