A complex macro definition

[samzcs]

define blHeadTable ((V_ROM1_FAR tblHead V_ROM2_FAR V_ROM3 *)(BL_HEAD_ADDRESS))

define GetblDID1() (blHeadTable->DID[1])

I am a little confused in the first macro declaration. Appreciate any explanation.

[Jochen Arndt]

Basically it casts the fixed address BL_HEAD_ADDRESS as a pointer to some type:

# define someTypeAddr ((someType *)(BL_HEAD_ADDRESS))

In your case the type is V_ROM1_FAR tblHead V_ROM2_FAR V_ROM3. Assuming that V_ROM1_FAR and V_ROM2_FAR are something like far *, the type is a pointer in V_ROM3 that points to a tblHead pointer. Effectively it will assign a pointer to a tblHead structure at a fixed address.

[samzcs]

I understand it's like:

# define someTypeAddr ((someType *)(BL_HEAD_ADDRESS))

But the type:

V_ROM1_FAR tblHead V_ROM2_FAR V_ROM3

I am still a little confused with it.

int a Char short, is that similar?

Thanks

[Jochen Arndt]

You have to lookup first how V_ROM1_FAR and V_ROM2_FAR are defined. Then it will be something like

far * tblHead far * V_ROM3

far is a compiler and platform specific keyword. See Far pointer - Wikipedia[^]. See also Cx51 User's Guide: Abstract Pointers[^] (I did not found a better link that explains such castings).

[samzcs]

Thanks, I understand it. Looked into V_ROM2_FAR V_ROM3, V_ROM2_FAR be defined as const, V_ROM3 blank