Philips P89LPC908 用户手册

2003 Dec 8     

12

P0.4 - P0.6

3, 7,8

I/O

Port 0:        Port 0 is an I/O port with a user-configurable output types. During reset Port 

0 latches are configured in the input only mode with the internal pullup 
disabled. The operation of port 0 pins as inputs and outputs depends upon 
the port configuration selected. Each port pin is configured independently. 
Refer to the section Port Configurations on page 35 and the DC Electrical 
Characteristics in the datasheet for details.

The Keypad Interrupt feature operates with port 0 pins.
All pins have Schmitt triggered inputs.
Port 0 also provides various special functions as described below.

8

I/O

Port 0 bit 4.

I

CIN1A Comparator 1 positive input.

I

Keyboard Input 4.

 

 

7

I/O

Port 0 bit 5.

I

CMPREFComparator reference (negative) input.

I

Keyboard Input 5.

3

I/O

Port 0 bit 6.

O

Comparator 1 output.

I

Keyboard Input 6.

P1.5

1

I

Port 1 bit 5. (Input only)

I

External Reset input during power-on or if selected via UCFG1. When 
functioning as a reset input a low on this pin resets the microcontroller, 
causing I/O ports and peripherals to take on their default states, and the 
processor begins execution at address 0. Also used during a power-on 
sequence to force In-Circuit Programming mode.

P3.0 - P3.1

4,5

I/O

Port 3         Port 3 is an I/O port with a user-configurable output types. During reset Port 

3 latches are configured in the input only mode with the internal pullups 
disabled. The operation of port 3 pins as inputs and outputs depends upon 
the port configuration selected. Each port pin is configured independently. 
Refer to the section Port Configurations on page 35 and the DC Electrical 
Characteristics in the datasheet for details.

All pins have Schmitt triggered inputs.
Port 3 also provides various special functions as described below:

5

I/O

Port 3 bit 0.

O

XTAL2   Output from the oscillator amplifier (when a crystal oscillator option is 

selected via the FLASH configuration).

 

O

CLKOUTCPU clock divided by 2 when enabled via SFR bit (ENCLK - TRIM.6). It can 

be used if the CPU clock is the internal RC oscillator, watchdog oscillator or 
external clock input, except when XTAL1/XTAL2 are used to generate clock 
source for the Real-Time clock/system timer.

4

I/O

Port 3 bit 1.

I

XTAL1 Input to the oscillator circuit and internal clock generator circuits (when 

selected via the FLASH configuration). It can be a port pin if internal RC 
oscillator or watchdog oscillator is used as the CPU clock source, AND if 
XTAL1/XTAL2 are not used to generate the clock for the Real-Time clock/
system timer.

V

SS

2

I

Ground: 0V reference. 

V

DD

6

I

Power Supply: This is the power supply voltage for normal operation as well as Idle and 
Power down modes.