The Godfather talking
You may crack software. How about me?
Sonsivri
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
December 10, 2016, 11:40:36 11:40


Login with username, password and session length


Pages: [1]
Print
Author Topic: 89c51 port epansion with 8255 keil c  (Read 3254 times)
0 Members and 1 Guest are viewing this topic.
Ronydc
Guest
« on: January 03, 2008, 11:38:13 11:38 »

 hi friends,

i wanted to increase the port pins with the help of 8255  for 89c51 mcu(atmel)

does any one have the c codes  that can work with keil  uvision (or c51 compiler).
i simply require a sample program with which if i  push a switch on any port pin of 89c51 and i can lit an LED connected on a single 8255 port pin.

your help can make a great fevour for me.
« Last Edit: January 03, 2008, 12:39:40 12:39 by metal » Logged
leptro
V.I.P
Junior Member
*****
Offline Offline

Posts: 61

Thank You
-Given: 240
-Receive: 20


« Reply #1 on: January 03, 2008, 04:18:22 16:18 »

hello,
i'am not a keil user nor a 8051 user, here's a link to the 8255 datasheet. http://www.datasheetarchive.com/pdf/496740.pdf
i've read it quickly and seems to be ease to interface.
good luck.
Logged
bugmike25
Junior Member
**
Offline Offline

Posts: 84

Thank You
-Given: 15
-Receive: 13


« Reply #2 on: January 03, 2008, 07:10:32 19:10 »

It is quite simple all u need to do is declare the ports of the 8255:

Usually this is used:

//First 8255 IC
#define porta1 XBYTE [0x8000]
#define portb1 XBYTE [0x8001]
#define portc1 XBYTE [0x8002]
#define cword1 XBYTE [0x8003]

// Second 8255 IC
#define porta2 XBYTE [0x9000]
#define portb2 XBYTE [0x9001]
#define portc2 XBYTE [0x9002]
#define cword2 XBYTE [0x9003]

//Then set the port functions - input, output etc. See datasheet for more info. example:
cword1 = 0x80;
//Add short delay here


porta1 = 0xff;
etc...............

Logged
Ronydc
Guest
« Reply #3 on: January 03, 2008, 07:36:30 19:36 »

 thanks leptro and bugmike25.

bug, its a nice thing that you have suggested but this do not work with keil. --> xbyte[0x .... ]  // even if we use the absacc.h  header file.

i found out that _at_  key word works well with keil.

like -->  char xdata PA _at_ 0x8000;
            char xdata CR _at_ 0x8003;
and we can take xdata char as-->
            char xdata j;

so that we can put,
void initPPI()
{ /
CR = 0x80; /* set all port for output */
}   

main()
{
while(1)
{
j = PA; /* read total port A into j*/
}
}

now my problem is..  how to read (or write onto) ON A SINGLE PIN of the port..?
can some one try for the code to push a switch on port pin P0.1 and lit an LED on 8255 port pin PA .2  ...?

PLEASE HELP.
THANKS

Logged
bugmike25
Junior Member
**
Offline Offline

Posts: 84

Thank You
-Given: 15
-Receive: 13


« Reply #4 on: January 03, 2008, 07:42:59 19:42 »

It works for sure with Keil. What version are u using? I use uVision3. You must include that header file:

#include <absacc.h>
Logged
Ronydc
Guest
« Reply #5 on: January 03, 2008, 07:45:51 19:45 »

i am using uvision2... any way. but still my problems stands.
what to do  for the access for a single port pin as i have write in the last paragraph.
Logged
bugmike25
Junior Member
**
Offline Offline

Posts: 84

Thank You
-Given: 15
-Receive: 13


« Reply #6 on: January 03, 2008, 08:02:37 20:02 »

I just found a more recent source code which isnt mine which uses the commands u used.  They only work with the recent versions of Keil (after ARM bought Keil) because i have an older version and that command does not work.

Now if u need to output on port A, pin 2 of the 8255 u must set ur control word to 1000XXXX = 0x80

This means that the 8255 is set to mode 0: basin i/o operation and port A is set as output.
Now when u are dealing with a port is must be treated at a byte.  Therefore if u need to use another pin on Port A for a completely different application you can do this:

Create a variable of unsigned char temp=0,
Then use a variable of type bit to set the state of ur LED; name it LED1,
Then set temp = temp|LED1;
and then shift left using the << command to place the bit in the correct position. This can be done for many different LEDx states.

Then using portA = temp;

However, u cannot just set a single bit on the 8255, you must treat is as a byte.


Logged
Ronydc
Guest
« Reply #7 on: January 03, 2008, 08:27:38 20:27 »

THX BUG ,
in short i got it, that as you said, the same can be done in following way.
if i want to lit a single led on any port pin.. i have to put there a port value.
like PA = 0X10;  or PA = 20; ( this is ment for some pins on and some off..)
and like tht the port value for the  required port pin.
yes.. this enlitans my mind... dear friend..!!

THANKS.

thanks a lot for your quick helps.
Logged
sjn
Guest
« Reply #8 on: January 12, 2008, 06:01:26 18:01 »

#define LCD_DATA     XBYTE [0xE000] // Port A
#define KEY_OUT      XBYTE [0xE001] // Port B
#define KEY_IN        XBYTE [0xE002] // Port C
#define CONTROL_PORT     XBYTE [0xE003] // Control Port

#define CONTROL_WORD   0x89  // Port A => O/P , B => O/P , C => I/P



.....

void main(void)
{
   unsigned char j;
   delay(1000);

   CONTROL_PORT = CONTROL_WORD;
             ...
             LCD_DATA  = 0x00;
}
Logged
Ronydc
Guest
« Reply #9 on: January 29, 2008, 08:57:22 20:57 »

we had a good discussion abt 8255 ports and pins . thanks friends.

but i have found the shortest way for solving my fundamental problem. and that is--> to use the switches in matrix form. i can use as many switches i like if thay are in matrix.
and the output too i suppose.
thanks any way.
Logged
Pages: [1]
Print
Jump to:  


DISCLAIMER
WE DONT HOST ANY ILLEGAL FILES ON THE SERVER
USE CONTACT US TO REPORT ILLEGAL FILES
ADMINISTRATORS CANNOT BE HELD RESPONSIBLE FOR USERS POSTS AND LINKS

... Copyright 2003-2999 Sonsivri.to ...
Powered by SMF 1.1.18 | SMF © 2006-2009, Simple Machines LLC | HarzeM Dilber MC