Computer Architecture Assignment

LOOP: LODD PasCnt: ; num of fibs to do in PasCnt

JZER DONE: ; no more passes, go to done

SUBD c1:

STOD PasCnt: ; - - passes remaining

P1: LODD daddr: ; load a pointer to fib arg

PSHI ; push arg for fib on stack

ADDD c1:

STOD daddr: ; inc, store pointer for next d[n]

CALL FIB: ; call fib (arg on stack)

INSP 1 ; clear stack on fib return

P2: PUSH ; put return AC (fib(n)) on stack

LODD faddr: ; load a pointer to result f[n]

POPI ; pop result off stack into f[n]

ADDD c1:

STOD faddr: ; inc, store pointer for next f[n]

JUMP LOOP: ; go to top for next pass

FIB: LODL 1 ; fib func loads arg from stack

JZER FIBZER: ; if fib(0) go to FIBZER

SUBD c1: ; dec arg value in AC (arg-1)

JZER FIBONE: ; if fib(1) go to FIBONE

STOD LpCnt: ; number of iterations in LpCnt

LODD c0: ; load a 0 into the AC

STOD fm2: ; store 0 in fib(n-2)

LODD c1: ; load a 1 into the AC

STOD fm1: ; store 1 in fib(n-1)

ITER: LODD LpCnt: ; LpCnt arg - 1 iterations needed

JZER RTN: ; when LpCnt == 0 goto RTN:

SUBD c1: ; dec arg value in AC (LpCnt-1)

STOD LpCnt: ; store LpCnt for next iteration

LODD fm2: ; arg must be >= 2, fm2 initially fib(0)

ADDD fm1: ; fm1 initially fib(1), so AC = fm2+fm1

STOD tmp: ; store this AC to tmp:

LODD fm1: ; now load AC with fib(n-1)

STOD fm2: ; replace old fib(n-2) with AC

LODD tmp: ; load AC with tmp: becomes fib(n-1)

STOD fm1: ; store AC as next fib(n-1) to fm1

JUMP ITER: ; jump to next iteration

RTN: LODD tmp: ; load AC with tmp: .. final result

RETN

FIBZER: LODD c0:

RETN ; AC = 0 for fib(0)

FIBONE: LODD c1:

RETN ; AC = 1 for fib(1)

DONE: HALT

.LOC 100 ; locate data beginning at 100

d0: 3 ; array of args for fib function

9

18

23

25

f0: 0 ; array of result locs for fib returns

0

0

0

0

daddr: d0: ; start address of fib args

faddr: f0: ; start address of fib results

c0: 0 ; constants

c1: 1

PasCnt: 5 ; number of data elements to process

LpCnt: 0 ; number of fib iterations

tmp: 0 ; initial value for fib(2)

fm1: 0 ; at any point fib(n-1)

fm2: 0 ; at any point fib(n-2)