T89C51AC2-RLSI-M datasheet(4/117 Pages) ATMEL

4 / 117 page

Draft.A - March 30, 2001

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T89C51AC2

Table 1. Pin Description

Pin Name

Type

Description

VSS

GND

Circuit ground potential.

VCC

Supply voltage during normal, idle, and power-down operation.

VAREF

Reference Voltage for ADC

VAGND

Reference Ground for ADC

P0.0:7

I/O

Port 0:

is an 8-bit open drain bi-directional I/O port. Port 0 pins that have 1’s written to them float, and in this

state can be used as high-impedance inputs. Port 0 is also the multiplexed low-order address and data

bus during accesses to external Program and Data Memory. In this application it uses strong internal pull-

ups when emitting 1’s.

Port 0 also outputs the code bytes during program validation. External pull-ups

are required during

program verification.

In the T89C51AC2 Port 0 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.

P1.0:7

I/O

Port 1:

is an 8-bit bi-directional I/O port with internal pull-ups. Port 1 pins can be used for digital input/output

or as analog inputs for the Analog Digital Converter (ADC). Port 1 pins that have 1’s written to them

are pulled high by the internal pull-up transistors and can be used as inputs in this state. As inputs, Port

1 pins that are being pulled low externally will be the source of current (IIL, on the datasheet) because

of the internal pull-ups. Port 1 pins are assigned to be used as analog inputs via the ADCCF register.

As a secondary digital function, port 1 contains the Timer 2 external trigger and clock input; the PCA

external clock input and the PCA module I/O.

P1.0 / AN0 / T2

Analog input channel 0,

External clock input for Timer/counter2.

P1.1 / AN1 / T2EX

Analog input channel 1,

Trigger input for Timer/counter2.

P1.2 / AN2 / ECI

Analog input channel 2,

PCA external clock input.

P1.3 / AN3 / CEX0

Analog input channel 3,

PCA module 0 Entry of input/PWM output.

P1.4 / AN4 / CEX1

Analog input channel 4,

PCA module 1 Entry of input/PWM output.

P1.5 / AN5 / CEX2

Analog input channel 5,

PCA module 2 Entry of input/PWM output.

P1.6 / AN6 / CEX3

Analog input channel 6,

PCA module 3 Entry of input/PWM output.

P1.7 / AN7 / CEX4

Analog input channel 7,

PCA module 4 Entry ot input/PWM output.

Port 1 receives the low-order address byte during EPROM programming and program verification. In the

T89C51AC2 Port 1 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.

P2.0:7

I/O

Port 2:

Is an 8-bit bi-directional I/O port with internal pull-ups. Port 2 pins that have 1’s written to them are

pulled high by the internal pull-ups and can be used as inputs in this state. As inputs, Port 2 pins that

are being pulled low externally will be a source of current (IIL, on the datasheet) because of the internal

pull-ups. Port 2 emits the high-order address byte during accesses to the external Program Memory and

during accesses to external Data Memory that uses 16-bit addresses (MOVX @DPTR). In this application,

it uses strong internal pullups when emitting 1’s. During accesses to external Data Memory that use 8 bit

addresses (MOVX @Ri), Port 2 transmits the contents of the P2 special function register.

It also receives high-order addresses and control signals during program validation.

In the T89C51AC2 Port 2 can sink or source 5mA. It can drive CMOS inputs without external pull-ups.

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