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Message |
nirmal1990
Joined: 17 Nov 2016
Posts: 7
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| PIC 12F1840 EEPROM issue |
 Posted: Fri Nov 25, 2016 7:29 am |
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Hello,
I am working with PIC12F1840 and have a problem with EEPROM.
I am trying to run a startup function only 3 times so i need a non-volatile variable.
I am trying to store a variable in EEPROM.
But it is not working.
| Code: |
/*
#rom 0x7FFF = {1}
#define ADDR 0x7FFF
int8 stcnt =0;
*/
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| Code: |
/*
stcnt = read_eeprom(ADDR);
if(stcnt <= 0x02)
{
Startup();
stcnt++;
write_eeprom(ADDR,stcnt);
}
*/
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Here startup function is not getting executed.
Can someone help me with the issue ?
Thank you |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Fri Nov 25, 2016 8:07 am |
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The EEPROM, is not 'at' address 0x7FFF. This is a 'trick' used in the hex file, when passing data to the programmer. Data stored at this address, is _programmed_ to the EEPROM.
Read the manual entry for read_eeprom:
| Code: |
value = read_eeprom (address)
address is an 8 bit or 16 bit int depending on the part
Reads a byte from the specified data EEPROM address. The address begins at 0 and the range depends on the part.
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Note the last line. Address begins at 0....
When writing or reading the EEPROM, using the internal code, the address used, is the location _inside the EEPROM_. Not the 'pseudo address' used for programming.
So:
| Code: |
/*
#rom 0x7FFF = {1}
#define ADDR 0
int8 stcnt =0;
*/
/*
stcnt = read_eeprom(ADDR);
if(stcnt <= 0x02)
{
Startup();
stcnt++;
write_eeprom(ADDR,stcnt);
}
*/
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nirmal1990
Joined: 17 Nov 2016
Posts: 7
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| Posted: Mon Nov 28, 2016 1:22 am |
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Hi
Thank you for the reply.
I tried the changes but still it is not working.
The statement "if(stcnt <= 0x02) " is not getting true.
As per my understanding the default EEPROM value is 0x00 right.
so is there some other issues?
I use following fuses:
| Code: | | #fuses INTRC_IO,PUT,BROWNOUT,NOMCLR,NOPROTECT,NOLVP,NOWDT |
Does this have an impact ?
Thank you. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Mon Nov 28, 2016 2:20 am |
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No.
The default erased EEPROM content is 0xFF
The line you showed:
#rom 0x7FFF = {1}
Would set it to 1, if you have this in your code. |
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nirmal1990
Joined: 17 Nov 2016
Posts: 7
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| Posted: Mon Nov 28, 2016 2:53 am |
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Hi,
I did not understand this
in CCS help its mentioned
#rom 0x2100={1,2,3,4,5,6,7,8}
so it is also a method to insert data right.
so is it ok if i dont include this statement, since iam using read_eeprom and write_eeprom functions ?.
Also i am not sure of the data eeprom address iam using.
#rom 0x7FFF = {1}
this statement writes 1 to 0x7FFF or to all locations ?
Thank you |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Mon Nov 28, 2016 3:03 am |
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First, I assumed you had checked the programming address as 0x7F00 to 0x7FFF. It may not be, and I'd have to check the programming data sheet to know. It is always far safer to use:
#ROM int8 getenv("EEPROM_ADDRESS") = {0x00, ....}
This will write to the defined programming address for the EEPROM on any particular chip.
It writes sequentially starting at the first byte. So:
{1} will just write 1 to the first byte
{1,2,3,4} will write 1 to the first byte, 2 to the second etc..
Different chips use different addresses. 0x2100, 0x7F00, 0x 7F000 etc..
If you wanted to use the last byte in a 256 byte EEPROM, then your write_eeprom instruction would use 0xFF as the address, and the code to initialise the EEPROM should use:
#ROM int8 (getenv("EEPROM_ADDRESS")+0xFF) = {0x00} |
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nirmal1990
Joined: 17 Nov 2016
Posts: 7
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| Posted: Mon Nov 28, 2016 3:17 am |
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Hi
That was helpful, still i have a doubt.
if i use
| Code: | | #ROM int8 getenv("EEPROM_ADDRESS") = {0x00} |
this means i write 0 to the first location right.
So every time when the PIC is switched ON it writes 0 to first location.
But i want a non-volatile variable
as i want my startup function to be run only for 3 times (ie 3 ON OFF cycles). So I want to store number of sartups in eeprom first location.
So if i assign 0 to first location, on every PIC ON OFF cycle it will execute startup function. Which is a problem.
So do you know any solution ?
Thank you |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19539
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| Posted: Mon Nov 28, 2016 4:18 am |
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No.
What is in the #ROM statement, is only written when the chip is programmed. |
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nirmal1990
Joined: 17 Nov 2016
Posts: 7
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| Posted: Mon Nov 28, 2016 4:30 am |
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Thank you,
It worked. |
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