p87lpc778-01 NXP Semiconductors, p87lpc778-01 Datasheet - Page 38

• Manufacturer Part Number: p87lpc778-01
• Description: P87lpc778 Cmos Single-chip 8-bit 80c51 Microcontroller With 128-byte Data Ram, 8 Kb Otp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 12378
Product data
8.9.4 Keyboard interrupt (KBI)
The Keyboard Interrupt function is intended primarily to allow a single interrupt to be
generated when any key is pressed on a keyboard or keypad connected to specific
pins of the P87LPC778, as shown in
up the CPU from Idle or Power-down modes. This feature is particularly useful in
handheld, battery powered systems that need to carefully manage power
consumption yet also need to be convenient to use.
The P87LPC778 allows any or all pins of port 0 to be enabled to cause this interrupt.
Port pins are enabled by the setting of bits in the KBI register, as shown in Tables
and 36. The Keyboard Interrupt Flag (KBF) in the AUXR1 register is set when any
enabled pin is pulled LOW while the KBI interrupt function is active. An interrupt will
generated if it has been enabled. Note that the KBF bit must be cleared by software.
Due to human time scales and the mechanical delay associated with keyswitch
closures, the KBI feature will typically allow the interrupt service routine to poll port 0
in order to determine which key was pressed, even if the processor has to wake up
from Power-down mode. Refer to
for details.
Table 35:
Not bit addressable; Reset value: 00H
Bit
Symbol
Fig 13. Keyboard interrupt.
KBI - Keyboard interrupt register (address 86H) bit allocation
KBI.7
7
KBI.7
KBI.6
KBI.5
KBI.4
KBI.3
KBI.2
KBI.1
KBI.0
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
P0.1
P0.0
Rev. 01 — 31 March 2004
KBI.6
6
KBI.5
5
Section 8.12 “Power reduction modes” on page 43
Figure
KBI.4
4
CMOS single-chip 8-bit microcontroller
(from IEN1
13. This interrupt may be used to wake
register)
EKB
KBI.3
3
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
(KBI interrupt)
KBI.2
P87LPC778
KBF
2
002aaa631
KBI.1
1
KBI.0
38 of 79
0
35