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AD7147 Datasheet(PDF) 30 Page - Analog Devices |
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AD7147 Datasheet(HTML) 30 Page - Analog Devices |
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30 / 71 page  Data Sheet AD7147 Rev. E | Page 29 of 70 INTERRUPT OUTPUT The AD7147 has an interrupt output that triggers an interrupt service routine on the host processor. The INT signal is on Pin 17 and is an open-drain output. There are three types of interrupt events on the AD7147: a CDC conversion-complete interrupt, a sensor touch interrupt, and a GPIO interrupt. Each interrupt has enable and status registers. The conversion- complete and sensor-touch (sensor-activation) interrupts can be enabled on a per-conversion-stage basis. The status registers indicate what type of interrupt triggered the INT pin. Status registers are cleared, and the INT signal is reset high during a read operation. The signal returns high as soon as the read address has been set up. CDC CONVERSION-COMPLETE INTERRUPT The AD7147 interrupt signal asserts low to indicate the completion of a conversion stage and that new conversion result data is available in the registers. The interrupt can be independently enabled for each conversion stage. Each conversion-stage-complete interrupt can be enabled via the STAGEx_COMPLETE_INT_ENABLE register (Address 0x007). This register has a bit that corresponds to each conversion stage. Setting this bit to 1 enables the interrupt for that stage. Clearing this bit to 0 disables the conversion-complete interrupt for that stage. The AD7147 interrupt should be enabled only for the last stage in a conversion sequence. For example, if there are five conver- sion stages, only the conversion-complete interrupt for STAGE4 is enabled. Therefore, INT only asserts when all five conversion stages are complete and the host can read new data from all five result registers. The interrupt is cleared by reading the STAGEx_ COMPLETE_INT_STATUS register located at Address 0x00A. Register 0x00A is the conversion-complete interrupt status register. Each bit in this register corresponds to a conversion stage. If a bit is set, it means that the conversion-complete interrupt for the corresponding stage was triggered. This register is cleared upon a read if the underlying condition that triggered the interrupt is not present. SENSOR-TOUCH INTERRUPT The sensor-touch interrupt mode is implemented when the host processor requires an interrupt only when a sensor is contacted. Configuring the AD7147 into this mode results in the interrupt being asserted when the user makes contact with the sensor and again when the user stops touching the sensor. The second interrupt is required to alert the host processor that the user is no longer contacting the sensor. The registers located at Address 0x005 and Address 0x006 are used to enable the interrupt output for each stage. The registers located at Address 0x008 and Address 0x009 are used to read back the interrupt status for each stage. Figure 40 shows the interrupt output timing during contact with one of the sensors connected to STAGE0 while operating in the sensor-touch interrupt mode. For a low limit configuration, the interrupt output is asserted as soon as the sensor is contacted and again after the user has stopped contacting the sensor. (Note that the interrupt output remains low until the host processor reads back the interrupt status registers located at Address 0x008 and Address 0x009.) The interrupt output is asserted when there is a change in the interrupt status bits. This can indicate that a user is touching the sensor(s) for the first time, the number of sensors being touched has changed, or the user is no longer touching the sensor(s). Reading the status bits in the interrupt status register shows the current sensor activations. 4 2 CONVERSION STAGE SERIAL READBACK INT OUTPUT 3 1 STAGE1 STAGE0 FINGER ON SENSOR FINGER OFF SENSOR 1USER TOUCHING SENSOR. 2ADDRESS 0x008 IS READ BACK TO CLEAR INTERRUPT. 3USER STOPS TOUCHING SENSOR. 4ADDRESS 0x008 IS READ BACK TO CLEAR INTERRUPT. Figure 40. Example of Sensor-Touch Interrupt |
Similar Part No. - AD7147_17 |
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Similar Description - AD7147_17 |
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