Datasheet

Sensors
Freescale Semiconductor, Inc. 22
MMA7660FC
SERIAL INTERFACE
Serial-Addressing
MMA7660FC operates as a slave that sends and receives data through an I
2
C 2-wire interface. The interface uses a Serial
Data Line (SDA) and a Serial Clock Line (SCL) to achieve bi-directional communication between master(s) and slave(s). A
master (typically a microcontroller) initiates all data transfers to and from the device, and generates the SCL clock that
synchronizes the data transfer.
Figure 7. 2-Wire Serial Interface Timing Details
The device’s SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7 kΩ, is required on
SDA. The device’s SCL line operates only as an input. A pull-up resistor, typically 4.7 kΩ, is required on SCL if there are multiple
masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output.
Each transmission consists of a START condition (Figure 7) sent by a master, followed by MMA7660FC's 7-bit slave address
plus R/W bit, a register address byte, one or more data bytes, and finally a STOP condition.
Figure 8. Start and Stop Conditions
Start and Stop Conditions
Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a
START (S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with
the slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for another
transmission.
Bit Transfer
One data bit is transferred during each clock tap. See Figure 9. The data on SDA must remain stable while SCL is high.
Figure 9. Bit Transfer
SCL
SDA
t
LOW
t
HIGH
t
F
t
R
t
HD STA
t
HD DAT
t
HD STA
t
SU DAT
t
SU STA
t
BUF
t
SU STO
ST ART
CONDIT IO N
ST O P
CONDIT IO N
REPEAT ED ST ART
CONDIT IO N
ST ART
CONDIT IO N
DATA LINE STABLE
DATA VALID
CHANGE OF
DATA ALLOWED
SDA
SCL
START
CONDITION
SDA
SCL
STOP
CONDITION
PS