Ram management / Hi

Dual purpose post,

First let me say Hi, I’m a new PIC user, migrating from the basic stamp.

Second is a question,
It may be my paranoia from the stamps but how does one keep up with the RAM usage?

I have been using statements like:

SOMEPIN VAR PORTB.0

Does the compiler just place PORTB.0 in the places I type SOMEPIN, like a CON, or is there a variable created because of that statement?

You have direct access to the pin.

Ioannis

Quote:

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Originally Posted by 124C41

SOMEPIN VAR PORTB.0

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Hi

That means "SOMEPIN" is just another name for PORTB.0

consider it as a compiler DIRECTIVE ... that doesn't change the produced code.

Compiler just replaces all the "SOMEPIN" strings it finds by the "PORTB,0" string ( it's assembler that is generated ...) so, once declared, you can use one or the other ... when you want in your program.

Alain

ok thanks

Is there an easy way to see the amount RAM used?

The manual says the compiler uses about 24 bytes for system variables, if the PIC has 256 Bytes RAM is it safe to assume that the user has (256 – 24 = ) 232 bytes to use for variables?

A simple way to check how much RAM is used/available is to open the .asm file generated
after compiling.

Example;

Code:

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DEFINE OSC 20

X VAR PORTB
Y VAR BYTE

loop:
  FOR Y = 0 TO 7
    HIGH 0          'Turn on LED connected to RB0
    Pause 50      'Delay for .5 seconds
    Low 0          'Turn off LED connected to RB0
    Pause 50      'Delay for .5 seconds
  NEXT Y
    GoTo loop      'Go back to loop and blink LED forever
    End

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File name blink.bas. Open blink.asm after compiling, and you'll see something like this;

Code:

---

#define                OSC                20

RAM_START                      EQU        00020h
RAM_END                        EQU        001EFh
RAM_BANKS                      EQU        00004h
BANK0_START                    EQU        00020h
BANK0_END                      EQU        0007Fh
BANK1_START                    EQU        000A0h
BANK1_END                      EQU        000EFh
BANK2_START                    EQU        00110h
BANK2_END                      EQU        0016Fh
BANK3_START                    EQU        00190h
BANK3_END                      EQU        001EFh
EEPROM_START                    EQU        02100h
EEPROM_END                      EQU        021FFh

R0                              EQU        RAM_START + 000h
R1                              EQU        RAM_START + 002h
R2                              EQU        RAM_START + 004h
R3                              EQU        RAM_START + 006h
R4                              EQU        RAM_START + 008h
R5                              EQU        RAM_START + 00Ah
R6                              EQU        RAM_START + 00Ch
R7                              EQU        RAM_START + 00Eh
R8                              EQU        RAM_START + 010h
FLAGS                          EQU        RAM_START + 012h
GOP                            EQU        RAM_START + 013h
RM1                            EQU        RAM_START + 014h
RM2                            EQU        RAM_START + 015h
RR1                            EQU        RAM_START + 016h
RR2                            EQU        RAM_START + 017h
_Y                              EQU        RAM_START + 018h

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PBP system variables are from R0 to RR2. Your Y variable is the last one at 018h.

Depending on how complex your BASIC program is, PBP might need to create a few
temporary variables. If it does these will show up in the .asm file like the ones above.

RAM_START and RAM_END will change depending on the PIC you compile for.

Thank you very much :)