Multiple Channel Capacitive Touch Sensor and LED Driver
Datasheet
Chapter 3 Communications
The CAP1014 communicates via the SMBus or I2C communications protocols.
APPLICATION NOTE: Upon power up, the CAP1014 will not respond to any SMBus communications for 10ms.
After this time, full functionality is available.
3.1
System Management Bus Protocol
The CAP1014 communicates with a host controller, such as an SMSC SIO, through the SMBus. The
SMBus is a two-wire serial communication protocol between a computer host and its peripheral
devices. A detailed timing diagram is shown in Figure 3.1. Stretching of the SMCLK signal is supported,
however the CAP1014 will not stretch the clock signal.
TLOW
THIGH
THD:STA
TSU:STO
TRISE
TFALL
SMCLK
TSU:STA
THD:STA
THD:DAT
TSU:DAT
SMDATA
TBUF
S
S
P
P - Stop Condition
P
S - Start Condition
Figure 3.1 SMBus Timing Diagram
3.1.1
3.1.2
SMBus Start Bit
The SMBus Start bit is defined as a transition of the SMBus Data line from a logic ‘1’ state to a logic
‘0’ state while the SMBus Clock line is in a logic ‘1’ state.
SMBus Address and RD / WR Bit
The SMBus Address Byte consists of the 7-bit client address followed by the RD / WR indicator bit. If
this RD / WR bit is a logic ‘0’, then the SMBus Host is writing data to the client device. If this RD / WR
bit is a logic ‘1’, then the SMBus Host is reading data from the client device.
The CAP1014-1 responds to the slave address 0101_000xb. The CAP1014-2 responds to slave
address 0101_100xb.
Multiple addressing options are available. For more information contact SMSC.
3.1.3
SMBus Data Bytes
All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.
SMSC CAP1014
Revision 1.65 (08-11-09)
DATA1S5HEET
SMSC [ SMSC CORPORATION ]
