MC9S08AW16CFUE Datasheet, PDF (162/324 Pages) Freescale Semiconductor, Inc – MC9S08AW60 Features

Chapter 9 Keyboard Interrupt (S08KBIV1)
9.4.2 KBI Pin Enable Register (KBI1PE)
R
W
Reset
7
KBIPE7
0
6
KBIPE6
5
KBIPE5
4
KBIPE4
3
KBIPE3
2
KBIPE2
0
0
0
0
0
= Unimplemented or Reserved
Figure 9-4. KBI Pin Enable Register (KBI1PE)
1
KBIPE1
0
0
KBIPE0
0
Table 9-3. KBI1PE Register Field Descriptions
Field
Description
7:0
KBIPE[7:0]
Keyboard Pin Enable for KBI Port Bits — Each of these read/write bits selects whether the associated KBI
port pin is enabled as a keyboard interrupt input or functions as a general-purpose I/O pin.
0 Bit n of KBI port is a general-purpose I/O pin not associated with the KBI
1 Bit n of KBI port enabled as a keyboard interrupt input
9.5 Functional Description
9.5.1 Pin Enables
The KBIPEn control bits in the KBI1PE register allow a user to enable (KBIPEn = 1) any combination of
KBI-related port pins to be connected to the KBI module. Pins corresponding to 0s in KBI1PE are
general-purpose I/O pins that are not associated with the KBI module.
9.5.2 Edge and Level Sensitivity
Synchronous logic is used to detect edges. Prior to detecting an edge, enabled keyboard inputs in a KBI
module 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.
The KBIMOD control bit can be set to reconfigure the detection logic so that it detects edges and levels.
In KBIMOD = 1 mode, the KBF status flag becomes set when an edge is detected (when one or more
enabled pins change from the deasserted to the asserted level while all other enabled pins remain at their
deasserted levels), but the flag is continuously set (and cannot be cleared) as long as any enabled keyboard
input pin remains at the asserted level. When the MCU enters stop3 mode, the synchronous edge-detection
logic is bypassed (because clocks are stopped). In stop3 mode, KBI inputs act as asynchronous
level-sensitive inputs so they can wake the MCU from stop3 mode.
MC9S08AW60 Data Sheet, Rev 2
162
Freescale Semiconductor