5

4247DS–SCR–03/07

AT83C21GC

P1.3

CC4

4 kV

I/O

Smart Card Interface Function

Card contact 4 – Pull-up medium must be less than 20KΩ

P1.4

CCLK

4 kV

O

Smart Card Interface Function

Card clock

P1.5

CRST

4 kV

O

Smart Card Interface Function

Card reset – Pull-up medium must be less than 20KΩ

P3.0

RxD

I

UART Function

Receive data input

P3.1

TxD

O

UART Function

Transmit data output.

P3.2

INT0

I/O

Input/Output Function

P3.2 is a bi-directional I/O port with internal pull-ups.

P3.3

INT1

I/O

Input/Output Function

P3.3 is a bi-directional I/O port with internal pull-ups.

P3.4

I/O

Input/Output Function

P3.4 is a bi-directional I/O port with internal pull-ups.

P3.5

CIO1

I/O

Alternate Card Function

Card I/O: Pull-up medium must be less than 20K

P3.6

CCLK1

DV

CC

O

LED function

These pins can be directly connected to the cathode of the standard LED without

external current limiting resistors. The typical current of each output can be

programmed by software to 2, 4 or 10 mA (LEDCON register).

P3.7

CRST1

DV

CC

I/O

Input/Output Function

P3.7 is a bi-directional I/O port with internal pull-ups.

RST

V

CC

I/O

Reset Input

Holding this pin low for 64 oscillator periods while the oscillatoris running resets the

is applied, whether or not the oscillator is running. This pin has an internal pull-up

resistor which allows the device to be reset by connecting a capacitor between this pin

and VSS. Asserting RST when the chip is in Idle mode or Power-down mode returns

the chip to normal operation. The output is active for at least 12 oscillator periods when

an internal reset occurs.

XTAL1

V

CC

I

Input to the on-chip Inverting Oscillator Amplifier

To use the internal oscillator, a crystal/resonator circuit is connected

to this pin. If an external oscillator is used, its output is connected to this pin.

XTAL2

O

Output of the on-chip Inverting Oscillator Amplifier

To use the internal oscillator, a crystal/resonator circuit is connected

to this pin. If an external oscillator is used, XTAL2 may be left unconnected.

PWR

Supply Voltage

LI

PWR

DC/DC Input

current for the pump charge of the DC/DC converter.

Table 1. Port Signal Description (Continued)

Port

Signal

Name

Internal

Power

Supply

ESD

Type

Description