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Emmanuel
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| write/read eeprom |
 Posted: Sat Jul 03, 2004 11:58 am |
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I am new in pic18f458 mcu. Now i learn how to use eeprom. I try to write code as show below. but the result is the data in each address that show is the the data that write finally.
| Code: | #include <18f458.h>
#fuses HS,NOPROTECT,NOWDT,NOCPD,WRTD
#use delay(clock=10000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <input.c>
main() {
byte data,address,new_dat;
write_eeprom(0x00,0x41);
write_eeprom(0x01,0x50);
write_eeprom(0x02,0x55);
printf("\rdata in eeprom at 0x00: %x \n\r",read_eeprom(0x00));
printf("\rdata in eeprom at 0x01: %x \r\n",read_eeprom(0x01));
printf("\rdata in eeprom at 0x02: %x \r\n",read_eeprom(0x02));
}
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The result is
data in eeprom at 0x00: 55
data in eeprom at 0x01: 55
data in eeprom at 0x02: 55
pcm programmer or anyone,could you suggest me why? And how can i force it? Thank you in advance.  |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jul 03, 2004 1:08 pm |
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Ideally, you shouldn't ask a question to me by name because
I might not be available or I might not know the answer, and
then others might be too shy to reply your post.
But to get to your question:
The first thing I noticed was WRTD in the #fuses statement.
If you check the data sheet, this fuse is in bit 7 of the CONFIG6H
register. If you then look at the at end of the .LST file generated
for your program, you see that the CCS WRTD fuse causes this
bit to be set = 0. According to the data sheet, this will Write Protect
the Data EEPROM. So if it was previously filled with 0x55 (perhaps
due to running a previous test program ?), then your code that
writes to EEPROM will not work. That's what you're seeing.
You should do these two things:
1. Remove the WRTD fuse.
2. Add a while(1); statement at the end of your program, to
prevent the program from falling off the end of main().
CCS puts a hidden Sleep instruction there, which, if it's executed,
will cause the PIC to shut down before the last two chars are
transmitted from your hardware USART. (ie., the \n and \r chars) |
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