PC312XDP512F0CFVR datasheet(516/1348 Pages) FREESCALE

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Chapter 12 Serial Peripheral Interface (S12SPIV4)

MC9S12XDP512 Data Sheet, Rev. 2.21

516

Freescale Semiconductor

SPI operation in wait mode is a conﬁgurable low power mode, controlled by the SPISWAI bit

located in the SPICR2 register. In wait mode, if the SPISWAI bit is clear, the SPI operates like in

run mode. If the SPISWAI bit is set, the SPI goes into a power conservative state, with the SPI clock

generation turned off. If the SPI is conﬁgured as a master, any transmission in progress stops, but

is resumed after CPU goes into run mode. If the SPI is conﬁgured as a slave, reception and

transmission of a byte continues, so that the slave stays synchronized to the master.

•

Stop mode

The SPI is inactive in stop mode for reduced power consumption. If the SPI is conﬁgured as a

master, any transmission in progress stops, but is resumed after CPU goes into run mode. If the SPI

is conﬁgured as a slave, reception and transmission of a byte continues, so that the slave stays

synchronized to the master.

This is a high level description only, detailed descriptions of operating modes are contained in

Section 12.4.7, “Low Power Mode Options”.

12.1.4

Block Diagram

Figure 12-1 gives an overview on the SPI architecture. The main parts of the SPI are status, control and

data registers, shifter logic, baud rate generator, master/slave control logic, and port control logic.

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