A beginner in 8051 needs pro advice! AT89S51

[-joe-]

a warm greeting to all of you all,

i am just learning micro controller and i face some assembly programming question for my assignment.

I am using AT89S51 with 2 X ULN2803 to generate alphabet A to Z on a 8X8 LED dot matrix display. My problem now is the are 3 buttons :

forward to display next char ---> PORT1.0
backward to display previous char ---> PORT1.1
auto disply all char sequently ---> PORT1.2

I am very confused how to write an assembly code for these 3 buttons.
i managed to generate a program and hex codes for all the alphabet , but i can't write out a proper code for the buttons... please help!!

your kindness will be highly appreciated.

 

[IanP]

Try somthing like this (assuming button pressed = 0V, button released = 5V):

Button_Loop:
MOV A, P1
JNB ACC.0, NextButton
JNB ACC.1, BackButton
JNB ACC.2, AutoButton
JB AutoBut, AutoButton
MOV B, #10h
DJNZ B, $
SJMP Button_Loop

NextButton: ; display next character
CLR AutoBut
code .....
LJMP Button_Loop

BackButton: ; display previous character
CLR AutoBut
code .....
LJMP Button_Loop

AutoButton: ; auto display
SETB AutoBut
code .....
SJMP Button_Loop

Regards,
IanP

 

[-joe-]

hey thankyou very much for the help

i really appreciate it!!

 

[WinterInJuly]

89C51 you have 2 external interrupt INT0 and INT1 but you can expand more 2 external interrupt using 2 timer. Set Timer to Counter Mode to count the even. when a pulse come from P3.4 or P3.5, the count resgister is increase. If the counter is 8bit, set TH0=ff, when a pulse comes, the Counter is overflow and an interrupt is trigged--
Connect your button to interrupt pins and write interrupt subroutines code, it is easier

 

[RollingEEE]

I want to do a similar project can you please show me your circuit diagram?

 

[brevor]

Download his file, the circuit diagram is there.

 

[RollingEEE]

ya, I know. I got the circuit.

Can any one explain why pull ups were used in uln2803?