ATtiny13 registers for general use

Projects Programming
21

This is why I wanted to circumvent using Rxx but use memory address for general purpose registers instead:

C:\Users\usr\AppData\Local\Temp\arduino_build_453957\sketch/tm1637tiny.S:48: undefined reference to r16'** **C:\Users\usr\AppData\Local\Temp\arduino_build_453957\sketch/tm1637tiny.S:50: undefined reference to r17'
C:\Users\usr\AppData\Local\Temp\arduino_build_453957\sketch/tm1637tiny.S:52: undefined reference to r18'** **C:\Users\usr\AppData\Local\Temp\arduino_build_453957\sketch/tm1637tiny.S:54: undefined reference to r19'

I dunno what to do, I have included #include <avr/io.h>...

22

This will help...

23

The AVR has several different "address spaces" that are accessible by different instructions.
The math, logic, and mov instructions use 0 to 31 to access the CPU "general purpose registers." These instructions can use "r0" to "r31" as names to address the registers, which makes your program a lot clearer.
There are also IO registers SEPARATE from the CPU registers, numbered from 0 to 63. These can be access by the IN and OUT instructions, and the first 32 can be accessed by some special purpose IO instructions like SBI and CBI.
There is an EEPROM address space, 0 to EEPROMsize, accessed via a peripheral.
There is a FLASH Memory address space, 0 to FLASHsize, accessible by the LPM instruction, and by the instruction decoder.)
Finally, there is a "Data" address space that goes from 0 to RAMEND that includes the CPU registers (at 0 to 31), the IO registers (IOREG 0 at 32, IOREG 63 at 95, and RAM at addresses 64 to 127 (on a tiny13. The transition points change for different chips. Some newer chips are "different.") The whole "data" address space can be accessed by the LD and ST instruction family, but they take two cycles and some are two instruction words long.

So...

    mov 18,7  ; move CPU register 7 to CPU register 18
    out 18,7  ; output CPU register 7 to IO register 18
    sbi 18,7  ; set bit 7 of IO register 18
    subi 18,7 ; subtract the value 7 from cpu register 18
    lds 18,7  ; move data memory 7 (aka cpu reg 7) to cpu register 18 (takes 2 cycles and 2 words.)

A bit confusing - which is why you really SHOULD use the symbolic names:

    mov r18,r7        ; move CPU register 7 to CPU register 18
    out PORTB,r7      ; output CPU register 7 to portb
    sbi PORTB,PB7     ; set bit 7 of portb
    subi r18,7        ; subtract the value 7 from cpu register 18
    lds r18,mydata    ; load ram location mydata into cpu reg 18

There are also a bunch of illegal combinations:

    mov 18,mydata  ; mov only does CPU reg to CPU reg.
    out 100,7  ; IO Register 100 is too big.
    sbi TIMSK0,7  ; TIMSK0 is an IOREG, but out-of-range for SBI.

I drew this at one point. It might help.

24

westfw:
A bit confusing - which is why you really SHOULD use the symbolic names:

Why I wanted to skip rxx and use register addresses: I've got this error message about undefined reference to rxx and thought that GCC cannt interpret rxx but then I realized that it was my mistake after all - I tried to put rxx instead of immediate value in ldi instruction - a nono.... So from now on, I'll use rxx like a normal person!

Thanx for help!