UM10267 Datasheet, PDF (10/16 Pages) NXP Semiconductors – PCA9698 demonstration board OM6281

NXP Semiconductors
UM10267
PCA9698 demonstration board OM6281
8.2 GPIO input
8.2.1 Polling mode
In polling mode, the host controller must read the input port registers at predetermined
intervals to check if an input has changed. Depending on the application, the interrupt
mode described in Section 8.2.2 may be a more efficient method of verifying changes of
state on the input pins.
1. Select Bank0 and verify that the default values are displayed.
2. Since the PCA9698 has a small pull-up on the I/O, a read on the Input Port 0 register
returns 0xFF.
3. Pull Port0.7 to a logic LOW.
4. Read the Input Port 0 register and verify that the Input Port 0 register reads 0x7F.
8.2.2 Interrupt mode
In interrupt mode the interrupt pin is toggled to signal the host controller when an input
change of state has been detected. The interrupt mask register specifies which signal is
allowed to generate an interrupt.
1. Select Bank1 and verify the default values are active.
2. Un-check the MSK7 and MSK6 bits in the Mask Interrupt 1 register.
3. With the aid of an external pull-down, pull Port1.6 and Port1.7 bits to a logic LOW.
4. Verify the INT light is illuminated on the board.
5. Toggle the MSK6 and MSK7 bits and verify the INT light goes off only when both bits
are masked.
6. Read the Input Port 1 register and verify the contents is now 0x3F and the INT light is
off.
7. Pull the IO1.7 signal HIGH and verify that the interrupt light is on.
8. Toggle the MSK6 bit and verify that the INT light remains on.
9. Read the Input Port 1 register and verify that the contents is 0xBF and the INT light is
off.
9. Application specific: LED blinking and dimming with the PCA9530 and
the PCA9698
9.1 Theory of operation
The PCA9698 has the capability to drive up to 40 LEDs (within certain power restrictions
on the package, which can be overcome with the use of FETs). To enhance the
application of the PCA9698, a PCA9530 can be used to drive the Output Enable (OE) pin
to blink and dim the output of the LEDs. A pattern with intermediate complexity can be
easily generated by combining the outputs of the PCA9530.
A 74LVC1G38GW NAND gate is used to demonstrate the OE polarity inversion (active
HIGH instead of default active LOW) of the PCA9698.
UM10267_1
User manual
Rev. 01 — 24 September 2008
© NXP B.V. 2008. All rights reserved.
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