HELLO
I FOUND THAT THERE IS A DIFFERENCE SPEED BETWEEN PORTC AND PORT B
atmega644p
voltage vcc 5v25 (under dont start) current consumption >100ma
first of all clock at 40mhz with external clock fuze 010000
program in basic (may be in asm it is faster)
do
portc=0
portc=255
loop
speed mesured at oscilloscop 2.69mhz the same for porta and portd
do
portb=0
portb=255
loop
speed mesured at oscilloscop 5.76mhz
the frequency is stable in all case
does it mean that it is possible to double the pixel number on screen or double the color resolution by adding a latch like 74573 for reach 16 bit color
what did you think about
DIFFERENCE SPEED PORTC VS PORTB
Re: DIFFERENCE SPEED PORTC VS PORTB
THIS CODE GIVE 2.88MHZ ON PORTD AND C at same time
DO
PORTC=0
NOP
PORTD=0
NOP
PORTC=255
NOP
PORTD=255
LOOP
IF THE NOP ARE not set then it don t work
DO
PORTC=0
NOP
PORTD=0
NOP
PORTC=255
NOP
PORTD=255
LOOP
IF THE NOP ARE not set then it don t work
Re: DIFFERENCE SPEED PORTC VS PORTB
IF I DISABLE INTERRUPTS ALL THE PORT OUTPUT A TTL SIGNAL AT 5.76MHZ
LET ABOUT 10MHZ BY PIXEL
LET ABOUT 10MHZ BY PIXEL
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Re: DIFFERENCE SPEED PORTC VS PORTB
I'm pretty sure at a hardware level PortB and PortC are just as fast as each other when using OUT in ASM.
Re: DIFFERENCE SPEED PORTC VS PORTB
If you are interested in that definitely try the existing stuff to get a feel for it first. The results you show for different port speeds must be some hard to predict quirk of whatever BASIC is in use there. Asm can be faster or smaller, but the main benefit is you know exactly how many cycles the code will turn into as you write it.