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C51: How calling library in fixed ROM from code in XRAM

Burgess Ko

I have a 8051 project which includes ROM and XRAM, both are used as code memory
The memory address and range is as follows

CODE Space
Main CODE at RAM C:0x0000 ~ C:0x2FFF
Lib  CODE at ROM C:0x3000 ~ C:0x3FFF

XDATA Space
    XDATA RAM  at X:0x0000 ~ X:0x0FFF

I want to build a library code by Keil C51, and put the library code in fixed ROM memory,
so the code in RAM is able to call the library routine in the existing ROM.
For example:

main.c in CODE RAM (C:0x0000 ~ C:0x2FFF)

main()
{
    int x, y, z;
    x = 1;
    y = 2;
    z = Add(x, y);
}

lib.c in CODE ROM (C:0x3000 ~ C:0x3FFF)

int Add(int x, int y)
{
    int z;
    z = x + y;
    return z;
}

int Sub(int x, int y)
{
    int z;
    z = x - y;
    return z;
}

My question is:
1. Is there easy way to tell Keil C51 where to call library code at (C:0x3000 ~ C:0x3FFF) ? If a lot of routines in library.

2. Is it possible to call library function with arguments ?

3. Can library routine use local variables ?

Thanks for your response

Parents
  • 0 in reply to Burgess Ko

    Well, notice that you have select a 8051 processor and Keil C51 as compiler.

    But the 8051 is not designed for use with the C programming language, and the Keil C51 have to break the back backwards to try to implement C for the processor.

    If you did spend looking at the documentation, you would know that the compiler+linker together tries to convert all parameters and local variables into shared global variables. Not so fun if you already have some magic code already stored in a flash area.

    Fill a struct with the values you want to send.
    Have a fixed RAM address where you store the pointer to this struct.

    Or switch to a processor architecture that is better suited for traditional stack/register passing of parameters.

    What you are trying to do is have two completely separate programs interact. So document the exact interface that the library part should export to the other program. And then implement that exact interface.

Reply
  • 0 in reply to Burgess Ko

    Well, notice that you have select a 8051 processor and Keil C51 as compiler.

    But the 8051 is not designed for use with the C programming language, and the Keil C51 have to break the back backwards to try to implement C for the processor.

    If you did spend looking at the documentation, you would know that the compiler+linker together tries to convert all parameters and local variables into shared global variables. Not so fun if you already have some magic code already stored in a flash area.

    Fill a struct with the values you want to send.
    Have a fixed RAM address where you store the pointer to this struct.

    Or switch to a processor architecture that is better suited for traditional stack/register passing of parameters.

    What you are trying to do is have two completely separate programs interact. So document the exact interface that the library part should export to the other program. And then implement that exact interface.

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