AT83C21GC
Table 1.
Port Signal Description (Continued)
Internal
Port
P1.3
Signal
Name
CC4
Power
Supply
CV
CC
ESD
4 kV
Type
I/O
Description
Smart Card Interface Function
Card contact 4 – Pull-up medium must be less than 20KΩ
Smart Card Interface Function
Card clock
Smart Card Interface Function
Card reset – Pull-up medium must be less than 20KΩ
UART Function
Receive data input
UART Function
Transmit data output.
Input/Output Function
P3.2 is a bi-directional I/O port with internal pull-ups.
Input/Output Function
P3.3 is a bi-directional I/O port with internal pull-ups.
Input/Output Function
P3.4 is a bi-directional I/O port with internal pull-ups.
Alternate Card Function
Card I/O: Pull-up medium must be less than 20K
LED function
P3.6
CCLK1
DV
CC
O
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).
Input/Output Function
P3.7 is a bi-directional I/O port with internal pull-ups.
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.
P1.4
CCLK
CV
CC
4 kV
O
P1.5
CRST
CV
CC
4 kV
O
P3.0
RxD
EV
CC
I
P3.1
TxD
EV
CC
O
P3.2
INT0
DV
CC
I/O
P3.3
INT1
EV
CC
I/O
P3.4
EV
CC
I/O
P3.5
CIO1
DV
CC
I/O
P3.7
RST
CRST1
DV
CC
V
CC
I/O
I/O
5
4247DS–SCR–03/07
ATMEL [ ATMEL CORPORATION ]
