Atmel STK200, Manual

Page: 27 / 40

STK200 Starter Kit 9-1
Section 9
Board Applications
9.1 Using Switches
and LEDs
The LEDs are connected through a 1K resistor network to Port B.
The switches are connected to Port D.
The switches and LEDs can be disconnected, if required. To use them, ensure that the
jumpers labeled Port B and Port D are closed. The board is also marked with the port
pin connection for each switch and LED.
9.1.1 Using 8-Pin Devices
with LEDs The port pins on the AT90S2323 and other 8-pin parts are not connected to the correctly
labeled LEDs due to layout constraints. The actual connections are shown in the table
below:
9.2 Configuring
Switches and
LEDs
The ports must be correctly set in software as input or output. This is accomplished by
setting the direction control registers to 0 for input and 1 for output. Typical set-up code
would be:
ldi r16,$ff ;load immediate into temp storage register
out DDRB,r16 ;PORTB (LED’s) is all outputs
ldi r16,$00 ;load immediate into temp storage register
out PORTB,r16 ;switch all the LEDs on
out DDRD,r16 ;set direction register to zeros for input
9.3 Using External
Connections
All the ports are brought out to headers on the edge of the board but there are differ-
ences for different sockets which are described separately. Port B has current limit
resistors for programming on Pin 7, Pin 6 and Pin 5 MOSI, MISO and SCK. These port
pins will only supply a reduced current if used as outputs—300 micro Amps @ 3.3V and
500 micro Amps @ 5V. As inputs, they will behave normally. Therefore, any user circuit
should use Port B for inputs.
Processor Pin LED Label Socket Pin Number
PB0 PB5 5
PB1 PB6 6
PB2 PB7 7
PB3 PB3 2
PB4 PB4 3