33993 Datasheet, PDF (11/28 Pages) Freescale Semiconductor, Inc – Multiple Switch Detection Interface

FUNCTIONAL DEVICE OPERATION
FUNCTIONAL PIN DESCRIPTION
FUNCTIONAL DEVICE OPERATION
MCU INTERFACE DESCRIPTION
The 33993 device directly interfaces to a 3.3 V or 5.0 V
microcontroller unit (MCU). SPI serial clock frequencies up to
6.0 MHz may be used for programming and reading switch
input status (production tested at 4.16 MHz). Figure 7
illustrates the configuration between an MCU and one 33993.
Serial peripheral interface (SPI) data is sent to the 33993
device through the SI input pin. As data is being clocked into
the SI pin, status information is being clocked out of the
device by the SO output pin. The response to a SPI
command will always return the switch status, interrupt flag,
and thermal flag. Input switch states are latched into the SO
register on the falling edge of the chip select (CS) pin.
Twenty-four bits are required to complete a transfer of
information between the 33993 and the MCU.
MC68HCXX
Microcontroller
Shift Register
MOSI
MISO
33993
SI
24-Bit Shift Register
SO
SCLK
Receive
Buffer
CS
Parallel
Ports
INT
INT
To Logic
Figure 7. SPI Interface with Microprocessor
Two or more 33993 devices may be used in a module
system. Multiple ICs may be SPI-configured in parallel or
serial. Figures 8 and 9 show the configurations. When using
the serial configuration, 48-clock cycles are required to
transfer data in / out of the ICs.
MC68HCXX
Microcontroller
Shift Register
MOSI
MISO
SCLK
Parallel
Ports
INT
33993
SI
SO
SCLK
CS
INT
33993
SI
SO
SCLK
CS
INT
Figure 8. SPI Parallel Interface with Microprocessor
MC68HCXX
Microcontroller
Shift Register
MOSI
MISO
SCLK
Parallel
Ports
INT
33993
SI
SO
SCLK
CS
INT
33993
SI
SO
SCLK
CS
INT
Figure 9. SPI Serial Interface with Microprocessor
Analog Integrated Circuit Device Data
Freescale Semiconductor
33993
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