PGA400-EP Datasheet, PDF (29/99 Pages) Texas Instruments – PRESSURE SENSOR SIGNAL CONDITIONER

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PGA400-EP
SLDS195B – MAY 2013 – REVISED FEBRUARY 2014
6.17.2 Activating and Deactivating the OWI Interface
6.17.2.1 OWI Activation Procedure
Figure 6-10 shows the sequence diagram for the OWI activation procedure. This figure shows that the
OWI master initiates the switching of the VOUT1/OWI pin from DAC output mode to OWI mode by
generating an OWI activation signal. Upon receiving the OWI activation signal, the PGA400 OWI controller
generates OWI_ACTIVATION interrupt to the 8051W. The user interrupt service routine switches the
VOUT1/OWI mode by writing to the appropriate registers.
OWI Master
PGA400
Hardware
PGA400
Software
VOUT1/OWI is in DAC Mode
Time
OWI Activation Signal
OWI Controller generates
OWI_ACTIVATION Interrupt
VOUT1/OWI is in OWI Mode
8051W User Software
changes VOUT1/OWI
pin by writing to
DI_CTRL register in the
OWI_ACTIVATION
interrupt service routine
OWI Activation
Figure 6-10. OWI Activation Sequence
6.17.2.2 OWI Activation Signal
If the device is operating in the normal operation where the DAC is active and I2C or SPI communication
modes are not enabled the following activation signal can be driven into the VOUT1/OWI pin to place it
into OWI communication mode. The process begins with driving the OWI_EN voltage on the VOUT1/OWI
pin. As soon as the DAC voltage exceeds 5.4 volts the DAC is switched off by by a comparator. Once the
pin voltage reaches the OWI_EN voltage threshold a deglitch timer begins. Once the pin voltage has been
asserted for a time greater than the deglitch time the OWI Activation Comparator transmits a logic 1 value
to the OWI Controller. Figure 6-11 illustrates the activation of the OWI interface.
This deglitch time is set by the OWI_DEGLITCH_SEL bit in the Digital Interface Control Register
(DI_CTRL), and has the following properties:
• OWI_DEGLITCH_SEL = ‘0’ → OWI Activation deglitch time = 1ms
• OWI_DEGLITCH_SEL = ‘1’ → OWI Activation deglitch time = 10ms
• The default value for OWI_DEGLITCH_SEL bit is ‘0’, which corresponds to deglitch time of 1ms.
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FUNCTIONAL DESCRIPTIONS
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