Skip to content

Latest commit

 

History

History
59 lines (46 loc) · 2.14 KB

examples.md

File metadata and controls

59 lines (46 loc) · 2.14 KB
Raw

Here is some example programs for VIRTUAL16

Fibonacci Series

; Calculate first 25 numbers of fibonacci series and write them into memory
; This program takes ~25000 cycles. For 1Mhz 6502 it means 1 / 40 second

MAIN:
    MOV #25, R0         ;16-BIT CAN REPRESENT 25th FIBONACCI NUMBER MAXIMUM
    MOV #0, R1          ;FIRST ARGUMENT
    MOV #1, R2          ;SECOND ARGUMENT
    MOV #0x30, R4       ;FIBONACCI SERIES STARTING POINT
    MOV R1, +@R4        ;MOV FIRST ARGUMENT TO ADDRESS HELD BY R3 THEN INCREMENT POINTER
    DEC R0
    MOV R2, +@R4        ;MOV SECOND ARGUMENT TO ADDRESS HELD BY R3 THEN INCREMENT POINTER
    DEC R0
FIBONACCI:
    MOV R2, R3          ;BACKUP N-1 VALUE
    ADD R1, R2          ;CALCULATE N
    MOV R2, +@R4        ;MOV N TO ADDRESS HELD BY R3 THEN INCREMENT POINTER
    MOV R3, R1          ;MOV N-1 TO N-2
    DEC R0              ;DECREMENT COUNTER (R0)
    BNE R0, FIBONACCI   ;IF COUNTER IS NOT ZERO BRANCH TO FIBONACCI
END:
    RET					;Return to 6502 mode

Assembled version

DB 0x70, 0x19, 0x00, 0x71, 0x00, 0x00, 0x72, 0x01, 0x00, 0x74, 0x30, 0x00, 0x08, 0x14, 0x19, 0x00, 
DB 0x08, 0x24, 0x19, 0x00, 0x04, 0x23, 0x11, 0x12, 0x08, 0x24, 0x04, 0x31, 0x19, 0x00, 0xe0, 0xf4, 
DB 0x00

Factorial

; Calculate 8! and write result into memory
; This program takes ~12500 cycles. For 1Mhz 6502 it means 1 / 80 second

MAIN:
    MOV #8, R0         ;16-BIT CAN REPRESENT 8 FACTORIAL MAXIMUM
    MOV #1, R1         ;FIRST ARGUMENT
    MOV #0x30, R3      ;FACTORIAL RESULT
FACTORIAL:
    INC R2              ;INCREASE MULTIPLIER
    UMUL R1, R2         ;MULTIPLY R1 AND R2
    MOV ML, R1          ;MOV MULTIPLY RESULT LSW TO R1
    CMP R2, R0
    BNE CR, FACTORIAL   ;IF COUNTER IS NOT ZERO BRANCH TO FIBONACCI
    MOV R1, @R3         ;COPY RESULT TO ADDRESS HELD BY R4
END:
    RET					;Return to 6502 mode

Assembled version

DB 0x70, 0x08, 0x00, 0x71, 0x01, 0x00, 0x73, 0x30, 0x00, 0x18, 0x20, 0x16, 0x12, 0x04, 0xc1, 0x17, 
DB 0x20, 0xed, 0xf6, 0x06, 0x13, 0x00

More to come