42 lines
1.7 KiB
Markdown
42 lines
1.7 KiB
Markdown
```
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& 'C:\Program Files (x86)\Arduino\hardware\tools\avr\bin\avr-objdump.exe' -S "C:\\Users\\Lehtinen\\AppData\\Local\\Temp\\arduino_build_119176/test.ino.elf" > c:\temp\koe.txt
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```
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```
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cli // 1 clock
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PORTB = *ptr; // is this atomic? probably, because ptr is 6-bit pointer. nope...
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f98: e0 91 26 01 lds r30, 0x0126 ; 0x800126 <__data_end> // 2 clocks
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f9c: f0 91 27 01 lds r31, 0x0127 ; 0x800127 <__data_end+0x1> // 2 clocks
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fa0: 80 81 ld r24, Z // 1 clock
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fa2: 85 b9 out 0x05, r24 ; 5 // 1 clock
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sei // 1 clock
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```
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500ns
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```
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cli
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mov r31, r1
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mov r30, gpior0
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ld r24, Z
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out 0x05, r24
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sei
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```
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375ns
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## using i/o space
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- Can be used with in/out (i/o space) or lds (data space = i/o address+0x20)?
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- Compiler can detect what space is used and uses correct address?
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- in/out is 1 cycle? lds 2 cycles?
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## register as variable
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- https://forum.arduino.cc/index.php?topic=43760.5
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- http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_regbind
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- volatile register unsigned char my_register asm("r2");
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- https://www.avrfreaks.net/forum/binding-variable-register
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## running code from ram
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- https://forum.arduino.cc/index.php?topic=425962.0
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- https://forum.arduino.cc/index.php?topic=470631.0
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- "AVRs are Harvard architecture CPUs, so they CANNOT run code out of RAM, so that directive can't possibly do anything of any value whatsoever."
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- "Yes, Harvard IS the reason. A Harvard CPU, by definition, has separate code and data memory spaces. They execute code from one memory, and fetch data from a different memory. What you're seeing is most likely the compiler pretending the directive can do what you want, but the linker doing the only thing it can do - putting that code in FLASH."
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