ZSSC3122 Datasheet, PDF (33/64 Pages) List of Unclassifed Manufacturers – Low Voltage Capacitive Sensor Signal Conditioner

ZSSC3122 Datasheet
3.6.3 I²C™ and SPI Commands
As detailed in Table 3.11, there are three types of commands which allow the user to interface with the
ZSSC3122 in the I²C™ or SPI modes.
Table 3.11 I²C™ and SPI Command Types
Type
Description
Data Fetch (DF)
Measurement Request (MR)
Calibration Commands
Used to fetch data in any digital mode
Used to start measurements in Sleep Mode
Used in Command Mode during the
calibration process
Communication
Supported
I²C™ and SPI
I²C™ and SPI
I²C™ Only
Reference
Sections
Section 3.6.4
Section 3.6.5
Section 4.2
3.6.4 Data Fetch (DF)
The Data Fetch (DF) command is used to fetch data in any digital output mode. With the start of communication
(for I²C™ after reading the slave address; for SPI at the falling edge of SS) the entire output packet will be loaded
in a serial output register. The register will be updated after the communication is finished. The output is always
scaled to 14 bits independent of the programmed resolution. The ordering of the bits is big-endian.
3.6.4.1. I²C™ Data Fetch
An I²C™ Data Fetch command starts with the 7-bit slave address and the 8^th bit = 1 (READ). The ZSSC3122 as
the slave sends an acknowledge (ACK) indicating success. The number of data bytes returned by the ZSSC3122
is determined by when the master sends the NACK and stop condition. Figure 3.10 shows examples of fetching
two and three bytes respectively. The full 14 bits of capacitive data are fetched in the first two bytes. The MSBs of
the first byte are the status bits.
If temperature data is needed, additional temperature bytes can be fetched. In Figure 3.10, the three-byte data
fetch returns 1 byte of temperature data (8-bit accuracy) after the capacitive data. A fourth byte can be fetched
where the six MSBs of the fetched byte are the six LSBs of a 14-bit temperature measurement. The last two bits
of the fourth byte are undetermined and should be masked off in the application.
© 2016 Integrated Device Technology, Inc.
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January 25, 2016