putting a variable into bit addressable memory.CW5.1

[stevec]

I've set up a structure of bits to serve as flags.
struct {
    unsigned char flag1:1
    unsigned char flag2:1
    unsigned char flag3:1
} flags

 How do I get this to sit in the bit addressable area of RAM?

[CrasyCat]

Hello

I assume you are using a HC08 CPU and you want to place the variable flags in the direct memory area (between 0x00 and 0xFF).

Am I right?

I also assume you are using a project created using the project wizard. Is that correct?

This is done as follows:

#pragma DATA_SEG __SHORT_SEG  MY_ZEROPAGE

struct {
    unsigned char flag1:1
    unsigned char flag2:1
    unsigned char flag3:1
} flags;

#pragma DATA_SEG DEFAULT

If you have an external declaration for this variable, make sure to declare it in the same section.

#pragma DATA_SEG __SHORT_SEG  MY_ZEROPAGE

extern struct {
    unsigned char flag1:1
    unsigned char flag2:1
    unsigned char flag3:1
} flags;

#pragma DATA_SEG DEFAULT

There is an alternate notation.

If you have the following definition in a header file, which is included in all project source file:

#pragma DATA_SEG __SHORT_SEG  MY_ZEROPAGE

#pragma DATA_SEG DEFAULT

You can then define the variable as follows:

struct {
    unsigned char flag1:1
    unsigned char flag2:1
    unsigned char flag3:1
} flags @"MY_ZEROPAGE";

The declaration will then look as follows:

extern struct {
    unsigned char flag1:1
    unsigned char flag2:1
    unsigned char flag3:1
} flags @"MY_ZEROPAGE";

CrasyCat

[stevec]

Thanks very much CrasyCat. That's exactly what I wanted. Works a treat.