MMA8450QT datasheet(18/57 Pages) FREESCALE

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Sensors

Freescale Semiconductor

MMA8450Q

Multiple Byte Read

When performing a multi-byte read or “burst read”, the MMA8450Q automatically increments the received register address

commands after a read command is received. Therefore, after following the steps of a single byte read, multiple bytes of data

can be read from sequential registers after each MMA8450Q acknowledgment (AK) is received until a NACK is received from

the Master followed by a stop condition (SP) signaling an end of transmission.

Single Byte Write

To start a write command, the Master transmits a start condition (ST) to the MMA8450Q, slave address ($1D) with the R/W bit

set to “0” for a write, the MMA8450Q sends an acknowledgement. Then the Master (MCU) transmits the address of the register

to write to, and the MMA8450Q sends an acknowledgement. Then the Master (or MCU) transmits the 8-bit data to write to the

designated register and the MMA8450Q sends an acknowledgement that it has received the data. Since this transmission is

complete, the Master transmits a stop condition (SP) to the data transfer. The data sent to the MMA8450Q is now stored in the

appropriate register.

Multiple Byte Write

The MMA8450Q automatically increments the received register address commands after a write command is received.

Therefore, after following the steps of a single byte write, multiple bytes of data can be written to sequential registers after each

MMA8450Q acknowledgment (ACK) is received.

Figure 11. I2C Timing Diagram

Table 10. I2C device Address Sequence

Command

[6:1]

Device Address

[0]

SA0

[6:0]

Device Address

R/W

8-bit Final Value

Read

001110

0x1C

0x39

Write

001110

0x1C

0x38

Read

001110

0x1D

0x3B

Write

001110

0x1D

0x3A

< Single Byte Read >

Master

Device Address [6:0]

SR Device Address [6:0]

NAK SP

Slave

Data [7:0]

< Multiple Byte Read >

Master

Device Address [6:0]

SR Device Address [6:0]

Slave

Data [7:0]

Master

NAK

Slave

Data [7:0]

< Single Byte Write >

Master

Device Address [6:0]

Data [7:0]

Slave

< Multiple Byte Write >

Master

Device Address [6:0]

Data [7:0]

Slave

Legend

ST: Start Condition

SP: Stop Condition

NAK: No Acknowledge

W: Write = 0

SR: Repeated Start Condition

AK: Acknowledge

R: Read = 1

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