Array processing arbitrarily AVR length

Question

There is an example, I will cite below. In general, understood, understood with memory, in general, everything is clear, but it is not clear how to do the task - so that the program processes an array of arbitrary length. There is such code:

.DSEG .ORG 0x60 arr: .BYTE 10 .CSEG ;сегмент кода rjmp Reset ;вектор прерывания, вызываемого по сбросу микроконтроллера Reset: ;начало программы ldi XH,HIGH(arr) ;указатель X проинициализирован значением ldi XL,LOW(arr) ;адреса начала массива arr ldi YH,HIGH(arr+10) ;указатель Y проинициализирован значением ldi YL,LOW(arr+10) ;адреса следующего за последним элементом массива arr ldi r16,5 ;загрузка в счетчик цикла r16 числа 5 cycle: ld r0,X ;копирование в r0 содержимого ячейки ОЗУ, на которую указывает X ld r1,-Y ;копирование в r1 содержимого ячейки ОЗУ, на которую ;указывает Y с предварительным уменьшением Y на единицу st Y,r0 ;копирование r0 в ячейку ОЗУ, на которую указывает Y st X+,r1 ;копирование r1 в ячейку ОЗУ, на которую указывает X ;с последующим увеличением X на единицу dec r16 ;r16<-(r16-1) cpi r16,0x00 ;сравнение r16 с нулем brne cycle ;повторение цикла, если не 0 rjmp PC ;бесконечный цикл

As I understood, on the basis of the condition, I need to make it so that I can put any number in arr: .BYTE **** and it was handled normally. So, somehow, it is necessary for Y to know the end, and then with the counter it will be easier to do this so that Y knows the end of the array?
Or do not dig in the wrong direction and think wrong?

And if you just put a label after arr: .BYTE 10 and initialize YH / YL with the address of this label?
Well .DSEG .ORG 0x60 arr: .BYTE 100 arrend: ... ldi YH, HIGH (arrend); the pointer Y is initialized with the value ldi YL, LOW (arrend); the addresses following the last element of the arr array
I don’t know yet how to “catch” the number (actually, from .byte), which I need to do, including with a counter.
ldi r16, (arrend-arr) / 2 In general, if this is not a learning task, then it is better to write in C (at least the gcc port for avr8. For winds it is called winavr)

microsin_to4ka_ru microsin_to4ka_ru 26 2 · Accepted Answer · 2012-11-06T10:51:40

In order for the program to process an array of arbitrary length, information about the length of the array is needed in any case. It must either be in the form of a separate number in which the length of the array is stored, or in the array itself there must be a sign of its end. For example, the ASCIIZ strings are encoded with the end sign — these strings are ordinary arrays of arbitrary length, which at the end of the array always have a zero element.

(The limit to comments on the question has been exhausted, so here) I looked at the pdf - help on avr assembler.

Array processing arbitrarily AVR length

1 answer 1

More articles: