Rainbow Electronics AT90LS4433 - Manual (Page 5)

5
AT90S/LS4433
1042G–AVR–09/02
Pin Descriptions
VCC Supply voltage.
GND Ground.
Port B (PB5..PB0) Port B is a 6-bit bi-directional I/O port with internal pull-up resistors. The Port B output
buffers can sink 20 mA. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated.
Port B also serves the functions of various special features of the AT90S4433 as listed
on page 73.
The Port B pins are tri-stated when a reset condition becomes active, even if the clock is
not running.
Port C (PC5..PC0) Port C is a 6-bit bi-directional I/O port with internal pull-up resistors. The Port C output
buffers can sink 20 mA. As inputs, Port C pins that are externally pulled low will source
current if the pull-up resistors are activated. Port C also serves as the analog inputs to
the A/D Converter.
The Port C pins are tri-stated when a reset condition becomes active, even if the clock is
not running.
Port D (PD7..PD0) Port D is an 8-bit bi-directional I/O port with internal pull-up resistors. The Port D output
buffers can sink 20 mA. As inputs, Port D pins that are externally pulled low will source
current if the pull-up resistors are activated.
Port D also serves the functions of various special features of the AT90S4433 as listed
on page 81.
The Port D pins are tri-stated when a reset condition becomes active, even if the clock is
not running.
RESET Reset input. An External Reset is generated by a low level on the RESET pin. Reset
pulses longer than 50 ns will generate a reset, even if the clock is not running. Shorter
pulses are not guaranteed to generate a reset.
XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit
XTAL2 Output from the inverting oscillator amplifier
AVCC AVCC is the supply voltage for Port A and the A/D Converter. If the ADC is not used,
this pin must be connected to V
CC
. If the ADC is used, this pin should be connected to
V
CC
via a low-pass filter. See page 64 for details on operation of the ADC.
AREF AREF is the analog reference input for the A/D Converter. For ADC operations, a volt-
age in the range 2.0V to AVCC must be applied to this pin.
AGND If the board has a separate analog ground plane, this pin should be connected to this
ground plane. Otherwise, connect to GND.