MMA7450LR2 datasheet(9/22 Pages) FREESCALE

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Sensors

Freescale Semiconductor

MMA7450L

is then driven high at the end of a transmission. SPC is the

Serial Port Clock which is also controlled by the SPI master.

SDI and SDO are the Serial Port Data Input and the Serial

Port Data Output. The SDI and SDO data lines are driven at

the falling edge of the SPC and should be captured at the

rising edge of the SPC.

Read and write register commands are completed in 16

clock pulses or in multiples of 8, in the case of a multiple byte

read/write.

SPI READ OPERATION

A SPI read transfer consists of a 1-bit Read/Write signal, a

6-bit address, and 1-bit don’t care bit. (1-bit R/W=0 + 6-bits

address + 1-bit don’t care). The data to read is sent by the

SPI interface during the next transfer. See Figure 11 and

Figure 12 for the timing diagram for an 8-bit read in 4 wire and

3 wire modes, respectively.

Figure 11. SPI Timing Diagram for 8-Bit Register Read

(4 Wire Mode)

Figure 12. SPI Timing Diagram for 8-Bit Register Read

(3 Wire Mode)

SPI WRITE OPERATION

In order to write to one of the 8-bit registers, an 8-bit write

command must be sent to the MMA7450L. The write

command consists of an MSB (0=read, 1=write) to indicate

writing to the MMA7450L register, followed by a 6-bit address

and 1 don’t care bit.

The command should then be followed the 8-bit data

transfer. See Figure 13 for the timing diagram for an 8-bit

data write.

Figure 13. SPI Timing Diagram for 8-Bit Register Write

(3 Wire Mode)

MMA7450LR2 Datasheet(PDF) 9 Page - Freescale Semiconductor, Inc