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tonkostz
Joined: 07 May 2011
Posts: 40
Location: Bulgaria
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| Store number in rom and than read it. |
 Posted: Wed Mar 05, 2014 2:31 am |
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I use
#rom #ROM 0x3FF0={1234} to store 04D2 to rom address 0x3FF0.
Hot to read 0x3FF0 address and if number is the same to perform some operation? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19498
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| Posted: Wed Mar 05, 2014 3:21 am |
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Question one, 'why bother'....
You do realise that if you declare a variable as 'const', it is stored in ROM for you, and can be used as a normal variable.
So:
| Code: |
const int16 ROM_val=1234;
if (ROM_val==1234)
//do something....
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'1234' is actually stored for you in ROM.
However if you 'must' store at a specific location, then use 'read_program_eeprom'
So:
| Code: |
#rom #ROM 0x3FF0={1234}
int16 ROM_val;
ROM_val=read_program_eeprom(0x3FF0);
if (ROM_val==1234)
//do something
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But _caveat_. What can be stored at a location depends on your chip. With a PIC16, each ROM 'word' is only 14 bits wide. So could store 0x3FFF, but not 0x7FFF.
Then some older chips _cannot_ read their own ROM. They just don't have the instructions to do this. If you code as the 'const', the compiler will instead generate a _program_ to return the correct values on such chips. If you use #ROM, it cannot be retrieved in such chips. |
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tonkostz
Joined: 07 May 2011
Posts: 40
Location: Bulgaria
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| Posted: Wed Mar 05, 2014 4:18 am |
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| Thanks Ttelmah! |
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