Daniel Rogers

Handling External RAM

Discussion created by Daniel Rogers on Dec 19, 2006
Latest reply on Dec 20, 2006 by CompilerGuru
How well does CW handle external RAM on the MC9S12DP256 processor.
This processor only has a PPage registor on dpage therefor code and ram are handled by the same register. I have used the ICC compiler for my code in the past and it didnt handle external RAM at all. I therefore had to do special code to deal with it.
#define pLocation 0x4003
#define newpage 0x10
coldpage = PORTK;
PORTK = newpage;
asm("nop"); // as PORTK requires an extra clock cycle to change correctly
*(int*)pLocation := 34;
PORTK = cOldPage;
in the code worrier I have decleared the RAM as such
   PAGE_10 = NO_INIT    0x104000 TO 0x107FFF;
   PAGE_11 = READ_WRITE 0x114000 TO 0x117FFF;
   PAGE_12 = READ_WRITE 0x124000 TO 0x127FFF;
   PAGE_13 = READ_WRITE 0x134000 TO 0x137FFF;
   PAGE_14 = READ_WRITE 0x144000 TO 0x147FFF;
   BATTERY_RAM                  INTO PAGE_11,PAGE_12,PAGE_13,PAGE_14,PAGE_15,PAGE_16,PAGE_17,
   PROGRAM_RAM                  INTO PAGE_10;
 uchar pLocation;
 pLocation = 34;
I am ok while the system is runnung but as soon as I turn the unit off the value is lost. The external memory is battery backed and it is working. As I can load my old Image craft code and it is stored.
Do I need to modify the datapage.c file so as when dealling with code it works on PORTK rather than the ppage register.