Question

Assembly Language
Define a 64-bit constant signed integer in Flash. Then, Write a subroutine count_1s that would count the number of 1s in a byte. The subroutine will receive the input parameter in A and return the result back in A. Use this subroutine to write a program that would count the number of 1s inside the 64-bit constant signed integer. Define a variable that would hold the total count of 1s.

(Application of Shift/Rotate instructions) (No specific Architecture)

Answer 1

Cloud plz check the code below.

Ldi zl, high(data*2)

ldi zl, low(data*2)

lpm r0, Z

srl ro, 3                  //Divide by 8 routine i.e right shift three times

mov r1,                   #0 (initialize R1 and R6 to zero)

mov r6,                    #0

count_1s: and r6, r6, r0, srl     #1 //Right shift by 1, right most bit is in carry flag)

addcs r1,                                    #1 //Add #1 to r1 if carry flag is set)

cmp r0,                                      #0 //update the status flags if r0 == 0 or not)

beq count_1s

// A.word can writes number 8 to flash memory

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