P87LPC768FD datasheet(30/64 Pages) PHILIPS

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Philips Semiconductors

Preliminary data

87LPC768

Low power, low price, low pin count (20 pin) microcontroller

with 4 kB OTP 8-bit A/D, Pulse Width Modulator

2001 Aug 06

BIT

SYMBOL

FUNCTION

P2M1.7

P2S

When P2S = 1, this bit enables Schmitt trigger inputs on Port 2.

P2M1.6

P1S

When P1S = 1, this bit enables Schmitt trigger inputs on Port 1.

P2M1.5

P0S

When P0S = 1, this bit enables Schmitt trigger inputs on Port 0.

P2M1.4

ENCLK

When ENCLK is set and the 87LPC764 is configured to use the on-chip RC oscillator, a clock

output is enabled on the X2 pin (P2.0). Refer to the Oscillator section for details.

P2M1.3

ENT1

When set, the P.7 pin is toggled whenever Timer 1 overflows. The output frequency is therefore

one half of the Timer 1 overflow rate. Refer to the Timer/Counters section for details.

P2M1.2

ENT0

When set, the P1.2 pin is toggled whenever Timer 0 overflows. The output frequency is therefore

one half of the Timer 0 overflow rate. Refer to the Timer/Counterssection for details.

P2M1.1, P2M1.0

—

These bits, along with the matching bits in the P2M2 register, control the output configuration of

P2.1 and P2.0 respectively, as shown in Table 4.

(P2M1.0)

SU01162

(P2M1.1)

ENT0

ENT1

ENCLK

P0S

P1S

P2S

P2M1

Reset Value: 00h

Not Bit Addressable

Address: A4h

Figure 16. Port 2 Mode Register 1 (P2M1)

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 87LPC768, as

shown in Figure 17. This interrupt may be used to wake 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 87LPC768 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 Figure 18. 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 the section on Power Reduction Modes for details.

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