MC68HC908RK2 Datasheet, PDF (83/158 Pages) Motorola, Inc – Microcontroller Unit

Chapter 7
Keyboard/External Interrupt Module (KBI)
7.1 Introduction
This section describes the maskable external interrupt (IRQ) input and six independently maskable
keyboard wakeup interrupt pins.
7.2 Features
Features of the KBI include:
• Dedicated external interrupt pin (IRQ)
• Six keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt
mask
• Internal pullup resistor
• Hysteresis buffer
• Programmable edge-only or edge- and level-interrupt sensitivity
• Automatic interrupt acknowledge
7.3 Functional Description
This section provides a functional description of the keyboard/external interrupt module (KBI).
7.3.1 External Interrupt
A logic 0 applied to the external interrupt pin (IRQ) can latch a CPU interrupt request. Figure 7-2 shows
the structure of the external (IRQ) interrupt of the KBI module.
A logic 0 applied to one or more of the keyboard interrupt pins can latch a CPU interrupt request.
Figure 7-5 shows the structure of the keyboard interrupts of the KBI module
See Figure 7-3 for a summary of the interrupt and keyboard input/output (I/O) registers.
Interrupt signals on the IRQ pin are latched into the IRQ latch. Keyboard interrupts are latched in the
keyboard interrupt latch. An interrupt latch remains set until one of these actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
IRQ latch and keyboard interrupt latch.
• Software clear — Software can clear an interrupt latch by writing to the appropriate acknowledge
bit in the interrupt status and control register (INTKBSCR). Writing a 1 to the ACKI bit clears the
IRQ latch. Writing a 1 to the ACKK bit clears the keyboard interrupt latch.
• Reset — A reset automatically clears both interrupt latches.
MC68HC908RK2 Data Sheet, Rev. 5.1
Freescale Semiconductor
83