EBI with S12Xep100. how to declare a variable in the external memory

[vijay_v]

Hi,

I am trying to get a Epson Display controller s1d13a05 interfaced to the s12xep100 chip (normal expanded mode operation). The 256K epson display controller's RAM is mapped to the CS0 range (starting at 0x400000)

I am using Codewarrior compiler and PE micro debugger

I am able to read and write to the display controller through a pointer (see below).

#define BASE_ADDRESS 0x400000
#define Display_Buffer (*(volatile unsigned char* far)(0x40000 + BASE_ADDRESS))

My question is how to declare a  variable in the mapped  external location. Below is the code which i am using. Please suggest me if there is any right way of doing this. Else should i change any compiler settings in the codewarrior.

#pragma DATA_SEG DISPLAY_RAM  //DISPLAY_RAM is defined in the linker .prm file for CS0 area
unsigned char far Display_Buffer[10][10];

the above code does not generate the GPAGE data properly.

Please help me.

Vijay V

[CompilerGuru]

Use the __GPAGE_SEG qualifier in the segment pragma:

Code:

#pragma DATA_SEG __GPAGE_SEG DISPLAY_RAM

 
Also: search for __GPAGE_SEG in this forum and there is also a good
technical note on the subject (don't know the number by heart)

If you do not want the compiler to zero out the DISPLAY_RAM,
place it in a NO_INIT segment in the prm.
In the prm you may have to use 0x400000'G as address, to explicitly state
the address is global.

Daniel

[vijay_v]

Daniel,

Thanks for your timely help. Really solved my problem Great

Also thanks for the NO_INIT hint.

Thanks again

Vijay