UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1013 of 1269
NXP Semiconductors
UM10503
Chapter 39: LPC43xx SSP0/1
If the SSP is enabled and there is valid data within the transmit FIFO, the start of
transmission is signified by the SSEL master signal being driven LOW. Master’s MOSI pin
is enabled. After a further one half SCK period, both master and slave valid data is
enabled onto their respective transmission lines. At the same time, the SCK is enabled
with a rising edge transition.
Data is then captured on the falling edges and propagated on the rising edges of the SCK
signal.
In the case of a single word transfer, after all bits have been transferred, the SSEL line is
returned to its idle HIGH state one SCK period after the last bit has been captured.
For continuous back-to-back transfers, the SSEL pin is held LOW between successive
data words and termination is the same as that of the single word transfer.
39.7.2.4 SPI format with CPOL = 1,CPHA = 0
Single and continuous transmission signal sequences for SPI format with CPOL=1,
CPHA=0 are shown in
.
In this configuration, during idle periods:
•
The CLK signal is forced HIGH.
•
SSEL is forced HIGH.
•
The transmit MOSI/MISO pad is in high impedance.
a. Single transfer with CPOL=1 and CPHA=0
b. Continuous transfer with CPOL=1 and CPHA=0
Fig 125. SPI frame format with CPOL = 1 and CPHA = 0 (a) Single and b) Continuous Transfer)
SCK
SSEL
Q
MSB
LSB
4 to 16 bits
MISO
MOSI
MSB
LSB
SCK
SSEL
MOSI
MISO
4 to 16 bits
4 to 16 bits
MSB
LSB
MSB
LSB
Q
MSB
LSB
Q
MSB
LSB