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benoit Joined: 24 Jul 2007 Posts: 177
Posted: Thu Jun 07, 2018 6:36 am Post subject: DIFFERENCE SPEED PORTC VS PORTB ATMEGA644P
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
WHY THIS DIFFERENCE ?
(BASCOM-AVR version : 2.0.7.3 , Latest : 2.0.8.1 )
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laborratte Joined: 27 Jul 2005 Posts: 299 Location: Berlin
Posted: Thu Jun 07, 2018 2:22 pm Post subject:
You really wonder that the chip does weird things when you run it way outside its specifications?
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benoit Joined: 24 Jul 2007 Posts: 177
Posted: Sun Jun 10, 2018 3:26 pm Post subject:
HELLO
IF I DISABLE INTERRUPT ALL THE PORTS RUN AT SAME FREQUENCY LET 5.76MHZ
LET ABOUT 11MHZ BY BYTES
GOOD
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