Hi all,
I wrote a program to test a 8051 microcontroller as follows.
.org 0000H
loop: mov P3, #000H
acall delay
mov P3, #0FFH
acall delay
ajmp loop
delay: mov R5, #005H
outloop2: mov R6, #0FFH
outloop1: mov R7, #0FFH
inloop: dec R7
cjne R7, #000H, inloop
dec R6
cjne R6, #000H, outloop1
dec R5
cjne R5, #000H, outloop2
ret
.end

I found that this program run correctly when I use a simulator. I stored it in an EPROM and put it in the circuit for runing. 8051 is connected with the EPROM through the address latch and connect data lines, address lines and control lines according to the INTEL microcontroller text book. LED bulbs are used for outputs. But when
the supply is given, out put is alwayas in high state ( Bulbs are ON). Initially I connected a crystal (4MHZ)with two capacitors as internal oscillator. Next I used a wave form generator with required values of voltage and frequency as an external clock. I did several changes but I got same results as earlier. Please reply and tell me how I correct it to get my results.