Atmel AVR AT90S8515-4 Bedienungsanleitung PDF herunterladen (Seite 16)

AN INTRODUCTION INTENDED FOR PEOPLE WITH NO PRIOR AVR KNOWLEDGE - AVRFREAKS.NET

Press [ F11 ]. DDRB is now 0xFF, As shown in the IO View above this is

represented as black squares in the IO View. So, a white square represents

logical low "0" and black squares are logical high "1". By setting DDRB high, all

bits of PORTB is configured as outputs.

Press [ F11 ]. 0xFF is now written to PORTB register, and the arrows points to the

DEC instruction. Note that PORTB is equal to 0xFF. Note also that the PINB

Press [ F11 ]. The Temp variable is decremented (0xFF - 1 = 0xFE). In addition

the PINB register changes from 0x00 to 0xFF! Why? To find out why this happens

you have to look at the PORT sections of the datasheet. The explanation is that

the PORTB is first latched out onto the pin, then latched back to the PIN register

giving you a 1 clock cycle delay. As you can see, the simulator behaves like the

actual part! The next instruction is a relative jump back to the Loop label.

Press [ F11 ]. The RJMP is now executed, and the arrow is back pointing at the

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Atmel AVR AT90S8515-4 Bedienungsanleitung Seite 16