5 and 6 Channel Capacitive Touch Sensor
Datasheet
3.4
SPI Interface (CAP1005 only)
The SMBus has a predefined packet structure, the SPI does not. The SPI Bus can operate in two
modes of operation, normal 4-wire mode and bi-directional 3-wire mode. The CAP1005 only supports
normal 4-wire mode. All SPI commands consist of 8-bit packets set to a specific slave device (identified
by the CS pin).
The SPI bus will latch data on the rising edge of the clock and the clock and data both idle high.
All commands are supported via both operating modes. The supported commands are: Reset Serial
interface, set address pointer, write command and read command. Note that all other codes received
during the command phase are ignored and have no effect on the operation of the device.
tP
tHIGH
tLOW
SPI_CLK
tFALL
tRISE
tSU:DAT
SPI_MSIO or
SPI_MOSI or
tD:CLK
tHD:DAT
SPI_MISO
Figure 3.1 SPI Timing
3.4.1
SPI Normal Mode
In the normal mode of operation, there are dedicated input and output data lines. The host
communicates by sending a command along the CAP1005 SPI_MOSI data line and reading data on
the SPI_MISO data line. Both communications occur simultaneously which allows for larger through
put of data transactions.
All basic transfers consist of two 8 bit transactions from the Master device while the slave device is
simultaneously sending data at the current address pointer value.
Data writes consist of two or more 8-bit transactions. The host sends a specific write command
followed by the data to write the address pointer. Data reads consist of one or more 8-bit transactions.
The host sends the specific read data command and continues clocking for as many data bytes as it
wishes to receive.
3.4.2
3.4.3
SPI_CS# Pin
The SPI Bus is a single master, multiple slave serial bus. Each slave has a dedicated CS pin (chip
select) that the master asserts low to identify that the slave is being addressed. There are no formal
addressing options.
Address Pointer
All data writes and reads are accessed from the current address pointer. In both Bi-directional mode
and Full Duplex mode, the Address pointer is automatically incremented following every read
command or every write command.
SMSC CAP1005 / CAP1006
Revision 1.1 (08-05-09)
DATA1S7HEET
SMSC [ SMSC CORPORATION ]
