MPR03X_09 Datasheet, PDF (4/32 Pages) Freescale Semiconductor, Inc – Proximity Capacitive Touch Sensor Controller

2.3 Serial Interface
The MPR03X uses an I²C Serial Interface. The I²C protocol implementation and the specifics of communicating with the Touch
Sensor Controller are detailed in the following sections.
2.3.1 Serial-Addressing
The MPR03X operates as a slave that sends and receives data through an I²C 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 MPR03X, and it generates the SCL clock that synchronizes
the data transfer.
The MPR03X SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7kΩ, is required on
SDA. The MPR03X SCL line operates only as an input. A pull-up resistor, typically 4.7kΩ, 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 5) sent by a master, followed by the MPR03X’s 7-bit slave address plus
R/W bit, a register address byte, one or more data bytes, and finally a STOP condition.
SDA
tSU _DAT
SCL
tHD _STA
tLOW
tHIGH
tR
tF
ST ART
CONDIT ION
tSU _STA
tHD _DAT
tHD _STA
REPEAT ED ST ART
CONDIT ION
tSU _STO
tBUF
STOP
ST ART
CONDIT ION CONDIT ION
Figure 5. Wire Serial Interface Timing Details
2.3.2 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.
SDA
SCL
DATA LINE STABLE
DATA VALID
CHANGE OF
DATA ALLOWED
Figure 6. Start and Stop Conditions
MPR03X
4
Sensors
Freescale Semiconductor