mc9s08qd4 Freescale Semiconductor, Inc, mc9s08qd4 Datasheet - Page 142

• Manufacturer Part Number: mc9s08qd4
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Keyboard Interrupts (S08KBIV2)
10.4
This on-chip peripheral module is called a keyboard interrupt (KBI) module because originally it was
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 up to eight 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).
10.4.1
Synchronous logic is used to detect edges. A falling edge is detected when an enabled keyboard interrupt
(KBIPEn=1) 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 (the deasserted level) during one bus cycle and then a logic 1 (the asserted level) during the next
cycle.Before the first edge is detected, all enabled keyboard interrupt input signals must be at the
deasserted logic levels. After any edge is detected, all enabled keyboard interrupt input signals must return
to the deasserted level before any new edge can be detected.
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.
10.4.2
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
142
KBEDGn
Field
7:0
Reset:
Functional Description
Keyboard Edge Selects — Each of the KBEDGn bits selects the falling edge/low level or rising edge/high level
function of the corresponding pin).
0 Falling edge/low level.
1 Rising edge/high level.
W
Edge Only Sensitivity
Edge and Level Sensitivity
R
KBEDG7
0
7
KBEDG6
0
6
Table 10-4. KBIES Register Field Descriptions
MC9S08QD4 Series MCU Data Sheet, Rev. 3
Figure 10-5. KBI Edge Select Register
KBEDG5
5
0
KBEDG4
0
4
Description
KBEDG3
0
3
KBEDG2
0
2
KBEDG1
0
1
Freescale Semiconductor
KBEDG0
0
0