10

AT89C5132

4173CS–USB–07/04

Table 11. A/D Converter Signal Description

Table 12. Keypad Interface Signal Description

Table 13. External Access Signal Description

Signal

Name

Type

Description

Alternate

Function

AIN1:0

I

A/D Converter Analog Inputs

-

AREFP

I

Analog Positive Voltage Reference Input

-

AREFN

I

Analog Negative Voltage Reference Input

This pin is internally connected to AVSS.

-

Signal

Name

Type

Description

Alternate

Function

KIN3:0

I

Keypad Input Lines

Holding one of these pins high or low for 24 oscillator periods triggers a

keypad interrupt.

P1.3:0

Signal

Name

Type

Description

Alternate

Function

A15:8

I/O

Address Lines

Upper address lines for the external bus.

Multiplexed higher address and data lines for the IDE interface.

P2.7:0

AD7:0

I/O

Address/Data Lines

Multiplexed lower address and data lines for the external memory or the

IDE interface.

P0.7:0

ALE

O

Address Latch Enable Output

ALE signals the start of an external bus cycle and indicates that valid

address information is available on lines A7:0. An external latch is used

to demultiplex the address from address/data bus.

-

ISP

I/O

ISP Enable Input

This signal must be held to GND through a pull-down resistor at the

falling reset to force execution of the internal bootloader.

-

RD

O

Read Signal

Read signal asserted during external data memory read operation.

P3.7

WR

O

Write Signal

Write signal asserted during external data memory write operation.

P3.6