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Two interrupt enable bits, TNEARIEN and RNFULLIEN, provide CPU interrupts based
on the "watermark" feature of the TNEARF and RNFULLF flags of the S register.
Address: Base a Bh offset
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
0
0
0
0
0
0
0
0
SPIx_C3 field descriptions
Field
Description
7–6
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
5
TNEAREF_
MARK
Transmit FIFO nearly empty watermark
This bit selects the mark after which the TNEAREF flag is asserted.
0
TNEAREF is set when the transmit FIFO has 16 bits or less
1
TNEAREF is set when the transmit FIFO has 32 bits or less
4
RNFULLF_
MARK
Receive FIFO nearly full watermark
This bit selects the mark after which the RNFULLF flag is asserted.
0
RNFULLF is set when the receive FIFO has 48 bits or more
1
RNFULLF is set when the receive FIFO has 32 bits or more
3
INTCLR
Interrupt clearing mechanism select
This bit selects the mechanism by which the SPRF, SPTEF, TNEAREF, and RNFULLF interrupts are
cleared.
0
These interrupts are cleared when the corresponding flags are cleared depending on the state of the
FIFOs
1
These interrupts are cleared by writing the corresponding bits in the CI register
2
TNEARIEN
Transmit FIFO nearly empty interrupt enable
Writing 1 to this bit enables the SPI to interrupt the CPU when the TNEAREF flag is set. This bit is ignored
and has no function if the FIFOMODE bit is 0.
0
No interrupt upon TNEAREF being set
1
Enable interrupts upon TNEAREF being set
1
RNFULLIEN
Receive FIFO nearly full interrupt enable
Writing 1 to this bit enables the SPI to interrupt the CPU when the RNFULLF flag is set. This bit is ignored
and has no function if the FIFOMODE bit is 0.
0
No interrupt upon RNFULLF being set
1
Enable interrupts upon RNFULLF being set
0
FIFOMODE
FIFO mode enable
This bit enables the SPI to use a 64-bit FIFO (8 bytes or four 16-bit words) for both transmit and receive
buffers.
0
FIFO mode disabled
1
FIFO mode enabled
Chapter 35 Serial Peripheral Interface (SPI)
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
587