5

P/N:PM0625 Specifications subject to change without notice, contact your sales representatives for the most update information. REV. 1.0, JUL. 01, 2005

MX10EXA

MNEMONIC

PIN. NO.

TYPE

NAME AND FUNCTION

PLCC

LQFP

P3.0-P3.7

11,13-19

5,7-13

I/O

Port 3: Port 3 is an 8-bit I/O port with a user configurable output type.

Port 3 latches have 1s written to them and are configured in the quasi-

bidirectional mode during reset. 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 on I/O port con-

figuration and the DC Electrical Characteristics for details.

Port 3 also provides various special functions as described below.

11

5

I

RxD0 (P3.0): Receiver input for serial port 0.

13

7

O

TxD0 (P3.1): Transmitter output for serial port 0.

14

8

I

INT0 (P3.2): External interrupt 0 input.

15

9

I

INT1 (P3.3): External interrupt 1 input.

16

10

I/O

T0 (P3.4): Timer 0 external input, or timer 0 overflow output.

17

11

I/O

T1/BUSW (P3.5): Timer 1 external input, or timer 1 overflow output.

The value on this pin is latched as the external reset input is released

and defines the default external data bus width (BUSW). 0 = 8-bit bus

and 1 = 16-bit bus.

18

12

O

WRL (P3.6): External data memory low byte write strobe.

19

13

O

RD (P3.7): External data memory read strobe.

RST

10

4

I

Reset: A low on this pin resets the microcontroller, causing I/O ports

and peripherals to take on their default states, and the processor to

begin execution at the address contained in the reset vector. Refer to

the section on Reset for details.

ALE

33

27

I/O

Address Latch Enable: A high output on the ALE pin signals external

circuitry to latch the address portion of the multiplexed address/data

bus. A pulse on ALE occurs only when it is needed in order to process

a bus cycle.

PSEN

32

26

O

Program Store Enable: The read strobe for external program memory.

When the microcontroller accesses external program memory, PSEN

is driven low in order to enable memory devices. PSEN is only active

when external code accesses are performed.

EA/WAIT

35

29

I

External Access/Wait/Programming Supply Voltage: The EA input

/VPP

determines whether the internal program memory of the microcontroller

is used for code execution. The value on the EA pin is latched as the

external reset input is released and applies during later execution. When

latched as a 0, external program memory is used exclusively, when

latched as a 1, internal program memory will be used up to its limit, and

external program memory used above that point. After reset is released,

this pin takes on the function of bus Wait input. If Wait is asserted high

during any external bus access, that cycle will be extended until Wait

is released. During EPROM programming, this pin is also the program-

ming supply voltage input.

XTAL1

21

15

I

Crystal 1: Input to the inverting amplifier used in the oscillator circuit

and input to the internal clock generator circuits.

XTAL2

20

14

O

Crystal 2: Output from the oscillator amplifier.