test2a-rom-led.asm

; test2a-rom-led
; assemble with: asm85 -b0000:00ff test2a-rom-led.asm
;
; Test program for 8085 SBC.  Blinks an LED on SOD forever.
; This program does not use any RAM or stack instructions, so it can be run
; from a ROM-only system as describled in Step 2 of the build instructions.
; Because it resides entirely in the first 256 bytes of ROM, an even simpler
; version of the hardware can be built where the A8..15 lines of the 8085 are
; left disconnected and the A8..A14 lines of the EEPROM are all connected to GND.

	    org 0000h

DLYTIM  equ 0ffffh      ; Delay loop for LED on and off times

START:
        mvi a, 0c0h     ; turn led on
        sim

		lxi h, DLYTIM	; pause
DELAY1:
        dcr l
		jnz DELAY1
        dcr h
        jnz DELAY1

        mvi a, 40h	    ; turn led off
        sim

        lxi h, DLYTIM   ; pause
DELAY2:
        dcr l
		jnz DELAY2
        dcr h
        jnz DELAY2

        jmp START	    ; Repeat forever