5
4247DS–SCR–03/07
AT83C21GC
P1.3 CC4 CV
CC
4 kV I/O
Smart Card Interface Function
Card contact 4 – Pull-up medium must be less than 20KΩ
P1.4 CCLK CV
CC
4 kV O
Smart Card Interface Function
Card clock
P1.5 CRST CV
CC
4 kV O
Smart Card Interface Function
Card reset – Pull-up medium must be less than 20KΩ
P3.0 RxD EV
CC
I
UART Function
Receive data input
P3.1 TxD EV
CC
O
UART Function
Transmit data output.
P3.2 INT0 DV
CC
I/O
Input/Output Function
P3.2 is a bi-directional I/O port with internal pull-ups.
P3.3 INT1 EV
CC
I/O
Input/Output Function
P3.3 is a bi-directional I/O port with internal pull-ups.
P3.4 EV
CC
I/O
Input/Output Function
P3.4 is a bi-directional I/O port with internal pull-ups.
P3.5 CIO1 DV
CC
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
device. The Port pins are driven to their reset conditions when a voltage lower than V
IL
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 V
CC
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.
V
CC
PWR Supply Voltage
V
CC
is used to power the internal voltage regulators and internal I/O’s.
LI PWR DC/DC Input
LI must be tied to V
CC
through an external coil (typically 4, 7 µH) and provide the
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
