SX8645I05AWLTRT Semtech, SX8645I05AWLTRT Datasheet - Page 20

• Manufacturer Part Number: SX8645I05AWLTRT
• Description: 12-ch Capacitive Touch Solution (Button & Wheel)
• Manufacturer: Semtech

SX8645
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (12 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
The QSM settings are fixed and can not be changed by the user.
In case the application needs different settings than the QSM settings then the SX8645 can be setup and/or
programmed over the I2C interface.
The configuration parameters of the SX8645 can be stored in the Multiple Time Programmable (MTP) Non
Volatile Memory (NVM). The NVM contains all those parameters that are defined and stable for the application.
Examples are the number of sensors enabled, sensitivity, active and Doze scan period. The details of these
parameters are described in the next chapters.
At power up the SX8645 checks if the NVM contains valid data. In that case the configuration parameter source
becomes the NVM. If the NVM is empty or non-valid then the configuration source becomes the QSM. In the next
step the SX8645 copies the configuration parameter source (QSM or NVM) into the Shadow Parameter Memory
(SPM). The SX8645 is operational and uses the configuration parameters of the SPM.
During power down or reset event the SPM loses all content. It will automatically be reloaded (from QSM or NVM)
following power up or at the end of the reset event.
The host will interface with the SX8645 through the I2C bus.
The I2C of the SX8645 consists of 16 registers. Some of these I2C registers are used to read the status and
information of the button and the wheel. Other I2C registers allow the host to take control of the SX8645. The host
can e.g. decide to change the operation mode from Active mode to Doze mode or go into Sleep (according to
Figure 8).
Two additional modes allow the host to have an access to the SPM or indirect access to the NVM.
These modes are required during development, can be used in real time or in-field programming.
Figure 19 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful
during the development phases of the application where the configuration parameters are not yet fully defined and
as well during the operation of the application if some parameters need to be changed dynamically.
Host SPM mode
Figure 19
The content of the SPM remains valid as long as the SX8645 is powered and no reset is performed. After a power
down or reset the host needs to re-write the SPM if relevant for the application.
Figure 20 shows the Host NVM mode. In this mode the host will be able to write the NVM.
Revision 7_5, February 10
© 2010 Semtech Corp.
www.semtech.com
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