• SPSCK
• The SPR3, SPR2, SPR1, and SPR0 baud rate selection bits in conjunction with
the SPPR2, SPPR1, and SPPR0 baud rate preselection bits in the SPI Baud Rate
register control the baud rate generator and determine the speed of the
transmission. The SPSCK pin is the SPI clock output. Through the SPSCK pin,
the baud rate generator of the master controls the shift register of the slave
peripheral.
• MOSI, MISO pin
• In master mode, the function of the serial data output pin (MOSI) and the serial
data input pin (MISO) is determined by the SPC0 and BIDIROE control bits.
• SS pin
• If C2[MODFEN] and C1[SSOE] are set, the SS pin is configured as slave select
output. The SS output becomes low during each transmission and is high when
the SPI is in idle state. If C2[MODFEN] is set and C1[SSOE] is cleared, the SS
pin is configured as input for detecting mode fault error. If the SS input becomes
low this indicates a mode fault error where another master tries to drive the
MOSI and SPSCK lines. In this case, the SPI immediately switches to slave
mode by clearing C1[MSTR] and also disables the slave output buffer MISO (or
SISO in bidirectional mode). As a result, all outputs are disabled, and SPSCK,
MOSI and MISO are inputs. If a transmission is in progress when the mode fault
occurs, the transmission is aborted and the SPI is forced into idle state. This
mode fault error also sets the Mode Fault (MODF) flag in the SPI Status Register
(SPIx_S). If the SPI Interrupt Enable bit (SPIE) is set when S[ MODF] gets set,
then an SPI interrupt sequence is also requested. When a write to the SPI Data
Register in the master occurs, there is a half SPSCK-cycle delay. After the delay,
SPSCK is started within the master. The rest of the transfer operation differs
slightly, depending on the clock format specified by the SPI clock phase bit,
CPHA, in SPI Control Register 1 (see
Note
A change of C1[CPOL], C1[CPHA], C1[SSOE], C1[LSBFE],
C2[MODFEN], C2[SPC0], C2[BIDIROE] with C2[SPC0] set,
SPIMODE, FIFOMODE, SPPR2-SPPR0 and SPR3-SPR0 in
master mode abort a transmission in progress and force the SPI
into idle state. The remote slave cannot detect this, therefore the
master has to ensure that the remote slave is set back to idle
state.
Chapter 35 Serial Peripheral Interface (SPI)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
589
Содержание MKL27Z128VFM4
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