Discussion in "Project Help" started by    Severus    Jun 5, 2007.
Tue Jun 05 2007, 01:19 PM
am studying microprocessors student , and i was looking at the next and found this question
can anybdy help me into where to start??

The question is attached as a pdf

[ Edited Fri Jun 08 2007, 10:41 AM ]
Tue Jun 05 2007, 02:54 PM
Hello severus.. nice to see your post on the forum. As i told you in the mail. you can start working on these project or assignments :-) one by one.
For now.. i think start from Timer and Calculator
I will you at each step where you feel stuck ok and after you complete it successfully. I will put it in my site.
In project A... first make the "As Timer" functionality.

» Now here is something you must do. make a routine which produce 1 sec delay.

Hint: see machine cycles of instruction you are using for perfect time delay and use 12MHz crystal. don't forget to include the machine cycle for Lcall instruction.

After you are done making that routine. make a small hardware which blinks an LED at a port with the delay routine u created. so you can check whether or not your routine is creating 1 sec delay or not.

I hope you will finish with this by tomorrow. I will guide you to the next step after this.
Tags timer and calculatortimerproject1 sec delay
Tue Jun 05 2007, 03:30 PM
i used a 74LS138, and i attached port 7 to a 74373 latch which s attached to the led , the program is

ledout:mov al,1
mov DX,373
out dx,al
JMP delay
delay:mov cx, 0fh
mov dx, 4240h
mov ah, 86h
int 15h
loop ledout
Tue Jun 05 2007, 04:21 PM
which processor/controller are you using. I am going to have dinner now. will come and tell you the next step think of something what you can do next.. then i will guide you :bye
Tue Jun 05 2007, 05:41 PM
the next part would be to Figure out how keypads work, it'll be a 4x3 matrix so I'm guessing i'll be looking at 7 inputs for the keypad unless i use some sort of IC between your microprocessor and the pad, i'll have two 7 segment LEDs for digits,and then i have four buttons as well, start, pause, stop, reset...

really missed up
Wed Jun 06 2007, 06:48 AM
don't be tense.. its not so hard
as we are doing the timer part right now.. so.. you just have to take care of four switches, which will be connected directly...
the start switch will be an interrupt switch and rest all switches (pause,stop,reset) will be polled when counting. hope you get my point.

» now the thing you suppose to do...
connect these four switches, start switch connected to interrupt pin and other three switches connected to normal pins.
make a program, at every interrupt you start blinking the LED and at stop stop the blinking led, and also pause will pause the blinking, leave the reset for the moment.

Hint: set a flag in interrupt routine which indicate that timer has to start now. and when you enter the timer routine, disable interrupt and start polling the three switches.

after this you are ready with all four switches. Complete this soon.

offtopic: sorry for last night, my internet was not working
Wed Jun 06 2007, 12:54 PM
i was working all day into the calc part, it seems easier

i have done a basic design
its attached
would you please see it and tell em what do u think
am using a 8086 processor , but the thing that i cannt figure out are
1- how to connect 2 7 sigma display togather
2-the led to show the minus sign???
how can u help please
3-the assemply code :S:S

[ Edited Wed Jun 06 2007, 12:55 PM ]
Wed Jun 06 2007, 12:57 PM
here is the attch
Wed Jun 06 2007, 02:45 PM
well.. the keypad stuff will take time to implement so i wanted you to work on timer first.
Port C of 8255 is bit addressable so connect rows of keypad to it, because its easy to drive and sense. Also it takes lesser time and easy programming.

Regarding connection of 2 7-segment displays, as you have the common anode pin is connected to +5V instead, connect it via transistor and transistor is switched with the help on Port C of 8255, so when you have two seven segments, you first send the data on first one and enable it, after sometime, disable it and enable the second one, when you do this switching faster, it looks like two numbers are getting displayed.
change your connections like this...

connect rows of Keypad to PC0-PC3, two common cathode pins are driven by PC4,PC5 and three switches are connected to PC6-PC8, Columns are connected to PB0-PB2 and seven segments are connected to PA0-PA7. LEDs can be connected to PA6 and PA7. The start button is connected to Interrupt pin. using PIC (programmable interrupt controller) i don't remember the IC i think its 8259. So whenever interrupt occurs the processor will set the flag and timer will start counting. I explained everything regarding what you have to do next... in the previous post

now i think your schematic part is over... please make a nice schematic.

so i hope you will do something.. regarding the above post.
Thu Jun 07 2007, 03:19 PM
OK, design is Done so far for the calculator part , now for the assembly program, i need too know how can i write an assembly program that reads the 2 numbers from the keypad? and then do the operations
(*=x , #=+, 0=-, and the keypad (1111) for /) , i know how can i display the result, i just dont know how can i do the math and read the number and the operation
i really cant thank u enough for your help :):):)

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