15.5.1 Port-E Keyboard Interrupt Functional Description

Writing to the KBEIE3–KBEIE0 bits in the keyboard interrupt enable register independently enables or disables each port E pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin in port-E does not enable its internal pullup device. Writing to the PEPE3–PEPE0 bits in the keyboard interrupt enable register independently enables or disables each port E pin pull-up device. A logic 0 applied to an enabled keyboard interrupt pin latches a keyboard interrupt request.

A keyboard interrupt is latched when one or more keyboard pins goes low after all were high. The MODEE bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt.

•If the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an interrupt request if another keyboard pin is already low. To prevent losing an interrupt request on one pin because another pin is still low, software can disable the latter pin while it is low.

•If the keyboard interrupt is falling edge- and low level-sensitive, an interrupt request is present as long as any keyboard pin is low.

If the MODEE bit is set, the keyboard interrupt pins are both falling edge- and low level-sensitive, and both of the following actions must occur to clear a keyboard interrupt request:

•

Vector fetch or software clear — A vector fetc h generates an

 

interrupt acknowledge signal to clear the interrupt request.

 

Software may generate the interrupt acknowledge signal by

 

writing a logic 1 to the ACKE bit in the keyboard status and control

 

register KBESCR. The ACKE bit is useful in applications that poll

 

the keyboard interrupt pins and require software to clear the

 

keyboard interrupt request. Writing to the ACKE bit prior to leaving

 

an interrupt service routine can also prevent spurious interrupts

 

due to noise. Setting ACKE does not affect subsequent transitions

 

on the keyboard interrupt pins. A falling edge that occurs after

 

writing to the ACKE bit latches another interrupt request. If the

 

keyboard interrupt mask bit, IMASKE, is clear, the CPU loads the

 

program counter with the vector address at locations $FFEC and

 

$FFED.

MC68HC(7)08KH12 — Rev. 1.1

Advance Information

 

 

 

 

Freescale Semiconductor

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MC68HC08KH12 specifications

The Freescale Semiconductor MC68HC08KH12 is a versatile microcontroller that has gained popularity in various embedded systems applications. Part of the HC08 family, this microcontroller combines a robust architecture with comprehensive on-chip features, making it suitable for a wide range of applications ranging from industrial control to consumer electronics.

One of the main features of the MC68HC08KH12 is its 8-bit architecture, which provides an optimal balance between performance and power efficiency. It operates at clock speeds of up to 2 MHz, allowing for efficient execution of instructions while maintaining low power consumption. The microcontroller is designed to operate over a voltage range of 2.7 to 5.5 volts, making it adaptable to various system requirements.

The MC68HC08KH12 is equipped with 1 Kbyte of RAM and 12 Kbytes of ROM, which allows for substantial program and data storage. The on-chip memory helps reduce the need for external components, simplifying the design of embedded systems and enhancing reliability. With a wide range of I/O options, including 26 general-purpose I/O pins, the microcontroller provides flexibility in interfacing with sensors, actuators, and other devices.

In terms of technologies, the MC68HC08KH12 features an advanced instruction set that enhances programming efficiency. It supports basic arithmetic operations, bit manipulation, and control transfer instructions, making it suitable for a variety of computational tasks. The integrated timers, analog-to-digital converters, and serial communication interfaces, including UART, provide the necessary tools for real-time control and data exchange with peripheral devices.

Another characteristic of the MC68HC08KH12 is its low power mode capabilities, which allow it to enter a sleep state during periods of inactivity. This feature is essential in battery-powered applications, where minimizing power consumption is crucial for extending operational life.

Overall, the Freescale Semiconductor MC68HC08KH12 stands out as a reliable microcontroller that combines performance, flexibility, and power efficiency. Its extensive features and technologies enable engineers to design robust embedded systems that meet the demands of modern applications. As a result, the MC68HC08KH12 remains a valuable choice for developers seeking a highly functional yet cost-effective microcontroller solution.
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