How to define constants that specify eeprom addresses

[Darrel Taylor]

Skip the EEPROM statement, and use DATA.

If you know the last used EEPROM location from the previous program.
Start somewhere after that with ...

DATA @128 ; anywhere past the original data

Then let PBP decide where the rest goes with ...

ee_patnum      DATA 2
ee_stepnum     DATA 0
ee_bright      DATA 255
ee_xfade       DATA 254

And when you want to retrieve it ...

READ ee_bright, bright
READ ee_xfade, xfade

Or write to it ...

WRITE ee_bright, bright
WRITE ee_xfade, xfade

If you have PBP 2.60, you can also have DATA Words or Longs.

hth,

[DwayneR]

Thanks, Darrel.

The main reason that I'm trying to do this symbolically is that the size (amount) of the user data changes. I simply want to maximize the amount of user space available, without having to re-calculate the system addresses when I change PICs.

Its a lot easier if I can just tell the compiler what the last address is and have it assign system variables automatically, starting from the top and working downwards.

Part of this learning exercise is developing the techniques I will be using in the future.

Your example helps a lot - I see how to assign symbol names to specific addresses. That makes it easy to re-write the code to avoid using hard-coded numeric constants as is done currently.

What I'd like to do now is have the addresses assigned automatically, if that is possible.

Any ideas?

Many thanks!

dwayne

[Darrel Taylor]

EEPROM allocation only increments.

And whether you're counting from end up or top down, you still need to know where the original program's highest EEPROM location is, and how many bytes you need now.

Going from end-up will make it longer before you overwrite locations, but it won't keep you from doing it.
If you start from the end of previous eeprom usage and add more as needed, then the compiler will let you know when you've run out.

But anyhow, if you know how many bytes you are adding(EEusedNow), and you know how many bytes are available ...

MaxEEPROM    CON 255
EEusedNow    CON 65

DATA  @MaxEEPROM - EEusedNow + 1

ee_patnum    DATA 2
ee_stepnum   DATA 0
ee_bright    DATA 255
ee_xfade     DATA 254

;... etc. ...

[DwayneR]

I think that will work quite nicely.

I know how many system variables that I have (not many) and I will certainly keep track of the user variables.

This does exactly what I want: provides me with a single place where I can specify the eeprom size.

Many thanks!

dwayne