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Table 39-5. UART Receiver with RTS Configuration (continued)
Register
Value
Comments
to received data with TIMOUT=0x2 and
TIMRST=0x4.
TIMCTLn
0x03C0_0081
Configure dual 8-bit counter using
inverted Pin 0 input. Trigger is internal
using inverted Pin 1 input.
TIMCMP(n+1)
0x0000_FFFF
Never compare.
TIMCFG(n+1)
0x0030_6100
Enable on Timer N enable and disable
on trigger falling edge. Decrement on
trigger to ensure no compare.
TIMCTL(n+1)
0x0143_0083
Configure 16-bit counter and output on
Pin 1. Trigger is internal using Shifter 0
flag.
SHIFTBUFn
Data to receive
Received data can be read from
SHIFTBUFBYS[7:0], use the Shifter
Status Flag to indicate when data can be
read using interrupt or DMA request.
Can support MSB first transfer by
reading from SHIFTBUFBIS[7:0] register
instead.
39.5.3 SPI Master
SPI master mode can be supported using two Timers, two Shifters and four Pins. Either
CPHA=0 or CPHA=1 can be supported and transfers can be supported using the DMA
controller. For CPHA=1, the select can remain asserted for multiple transfers and the
timer status flag can be used to indicate the end of the transfer.
The stop bit is used to guarantee a minimum of 1 clock cycle between the slave select
negating and before the next transfer. Writing to the transmit buffer by either core or
DMA is used to initiate each transfer.
Due to synchronization delays, the setup time for the serial input data is 1.5 FlexIO clock
cycles, so the maximum baud rate is divide by 4 of the FlexIO clock frequency.
Table 39-6. SPI Master (CPHA=0) Configuration
Register
Value
Comments
SHIFTCFGn
0x0000_0000
Start and stop bit disabled.
SHIFTCTLn
0x0083_0002
Configure transmit using Timer 0 on
negedge of clock with output data on Pin
0.
SHIFTCFG(n+1)
0x0000_0000
Start and stop bit disabled.
Table continues on the next page...
Chapter 39 FlexIO
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
775