NXP Semiconductors
FXTH87E
FXTH87E, Family of Tire Pressure Monitor Sensors
9 Keyboard Interrupt
The FXTH87E has a KBI module with general purpose I/O pins.
9.1 Features
The KBI features include:
• Up to four keyboard interrupt pins with individual pin enable bits.
• Each keyboard interrupt pin is programmable as falling edge (or rising edge) only, or
both falling edge and low level (or both rising edge and high level) interrupt sensitivity.
• One software enabled keyboard interrupt.
• Exit from low-power modes.
9.2 Modes of operation
This section defines the KBI operation in WAIT, STOP, and BACKGROUND DEBUG
modes.
9.2.1 KBI in STOP modes
The KBI operates asynchronously in STOP4 mode if enabled before executing the STOP
instruction. Therefore, an enabled KBI pin (KBPE[3:0]) can be used to bring the MCU out
of STOP4 mode if the KBI interrupt is enabled (KBIE = 1).
During STOP1 mode, the KBI is disabled. In some systems, the pins associated with
the KBI may be sources of wakeup from STOP1, see the STOP modes section in the
Section 5 "Modes of operation". Upon wakeup from STOP1 mode, the reset vector is
taken but no interrupt is generated (even if interrupt enabled).
The wake up is triggered when the pin is low (even with no edge), whatever the settings
are (raising edge or falling edge). So in STOP1 as long as the pin is low the reset vector
will be taken.
9.2.2 KBI in ACTIVE BACKGROUND mode
When the microcontroller is in ACTIVE BACKGROUND mode, the KBI will continue to
operate normally.
9.3 Block diagram
The block diagram for the keyboard interrupt module is shown in Figure 15.
FXTH87ERM
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© NXP B.V. 2019. All rights reserved.
Reference manual
Rev. 5.0 — 4 February 2019
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