SC9RS08KA2 datasheet(55/134 Pages) FREESCALE

55 / 134 page

Chapter 7 Keyboard Interrupt (RS08KBIV1)

SC9RS08KA2 Series Data Sheet, Rev. 1

Freescale Semiconductor

7.4

Functional Description

This on-chip peripheral module is called a keyboard interrupt (KBI) module because it was originally

designed to simplify the connection and use of row-column matrices of keyboard switches. However, these

inputs are also useful as extra external interrupt inputs and as an external means of waking the MCU from

stop or wait low-power modes.

The KBI module allows its pins to act as additional interrupt sources. Writing to the KBIPEn bits in the

keyboard interrupt pin enable register (KBIPE) independently enables or disables each KBI pin. Each KBI

pin can be configured as edge sensitive or edge and level sensitive based on the KBMOD bit in the

keyboard interrupt status and control register (KBISC). Edge sensitive can be software programmed to be

either falling or rising; the level can be either low or high. The polarity of the edge or edge and level

sensitivity is selected using the KBEDGn bits in the keyboard interrupt edge select register (KBIES).

Synchronous logic is used to detect edges. Prior to detecting an edge, enabled keyboard inputs must be at

the deasserted logic level. A falling edge is detected when an enabled keyboard input signal is seen as a

logic 1 (the deasserted level) during one bus cycle and then a logic 0 (the asserted level) during the next

cycle. A rising edge is detected when the input signal is seen as a logic 0 during one bus cycle and then a

logic 1 during the next cycle.

7.4.1

Edge Only Sensitivity

A valid edge on an enabled KBI pin will set KBF in KBISC. If KBIE in KBISC is set, an interrupt request

will be presented to the CPU. Clearing of KBF is accomplished by writing a 1 to KBACK in KBISC.

7.4.2

Edge and Level Sensitivity

A valid edge or level on an enabled KBI pin will set KBF in KBISC. If KBIE in KBISC is set, an interrupt

request will be presented to the CPU. Clearing of KBF is accomplished by writing a 1 to KBACK in

KBISC, provided all enabled keyboard inputs are at their deasserted levels. KBF will remain set if any

enabled KBI pin is asserted while attempting to clear by writing a 1 to KBACK.

7.4.3

KBI Pullup/Pulldown Device

The KBI pins does not automatically configure an internal pullup/pulldown device when a KBI pin is

enabled. An internal pull device can be used by configuring the associated I/O port pull device enable

7.4.4

KBI Initialization

When a keyboard interrupt pin is first enabled, it is possible to get a false keyboard interrupt flag. To

prevent a false interrupt request during keyboard initialization, the user should do the following:

1. Mask keyboard interrupts by clearing KBIE in KBISC.

2. If using internal pullup/pulldown device, configure the associated I/O port pullup/pulldown device.

3. Enable the KBI polarity by setting the appropriate KBEDGn bits in KBIES.

4. Enable the KBI pins by setting the appropriate KBIPEn bits in KBIPE.

SC9RS08KA2 датащи(PDF) 55 Page - Freescale Semiconductor, Inc

SC9RS08KA2 датащи(HTML) 55 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL