FXLS8471Q datasheet(19/75 Pages) FREESCALE

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FXLS8471Q

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Freescale Semiconductor, Inc.

6.2

SPI Interface characteristics

SPI interface is a classical master/slave serial port. The FXLS8471Q is always considered as the slave and thus is never initiating

the communication.

Table 9 and Figure 7 describe the timing requirements for the SPI system.

Figure 7. SPI Timing Diagram

6.2.1

General SPI operation

The CS_B pin is driven low at the start of a SPI transaction, held low for the duration of the transaction, and driven high after the

transaction is complete. During a transaction the master toggles the SPI clock (SCLK) and transmits data on the MOSI pin.

A write operation is initiated by transmitting a 1 for the R/W bit. Then the 8-bit register address, ADDR[7:0] is encoded in the first

and second serialized bytes. Data to be written starts in the third serialized byte. The order of the bits is as follows:

Byte 0: R/W,ADDR[6],ADDR[5],ADDR[4],ADDR[3],ADDR[2],ADDR[1],ADDR[0],

Byte 1: ADDR[7],X,X,X,X,X,X,X,

Byte 2: DATA[7],DATA[6],DATA[5],DATA[4],DATA[3],DATA[2],DATA[1],DATA[0].

Multiple bytes of DATA may be transmitted. The X indicates a bit that is ignored by the part. The register address is auto-

incremented so that the next clock edges will latch the data for the next register. When desired, the rising edge on CS_B stops

the SPI communication.

The FXLS8471Q SPI configuration is as follows:

•

Polarity: rising/falling

•

Phase: sample/setup

•

Order: MSB first

Data is sampled during the rising edge of SCLK and set up during the falling edge of SCLK.

Table 9. SPI timing

Function

Symbol

Min

Max

Unit

Operating Frequency

—

MHz

SCLK Period

tSCLK

1000

—

SCLK High time

tCLKH

500

—

SCLK Low time

tCLKL

500

—

CS_B lead time

tSCS

—

CS_B lag time

tHCS

—

MOSI data setup time

tSET

—

MOSI data hold time

tHOLD

—

MISO data valid (after SCLK low edge)

tDDLY

—

500

Width CS High

tWCS

100

—

CS_B

SCLK

MOSI

MISO

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