I am a using CodeWarrior version 5.7.0 with an MC9S12XDP512 processor.
I am trying to reserve 3 pages of paged RAM (FA, FB and FC) that will be accessed only by using far pointers. Basically I have a very basic file system that sequentially stores data to those pages of RAM and I want to be able to access that data later without it being overwritten. Whenever i try to write to memory, the contents of the memory say they are undefined.
I have declared the start addresses of my file system like this:
INT16U *__far startAddress = (INT16U*__far) 0xFA1000;
INT16U *__far endAddress = (INT16U*__far) 0xFC1FFF;
INT16U *__far currentAddress;
The addresses of each page are in the .prm file like this:
RAM_FA = READ_WRITE 0xFA1000 TO 0xFA1FFF ALIGN 2[1:1];
RAM_FB = READ_WRITE 0xFB1000 TO 0xFB1FFF ALIGN 2[1:1];
RAM_FC = READ_WRITE 0xFC1000 TO 0xFC1FFF ALIGN 2[1:1];
These 3 pages are reserved in this way:
PAGED_RAM /* paged data accessed by CPU12 only */
INTO RAM_FC, RAM_FB, RAM_FA;
One page was reserved for the X-Gate processor:
This is how I am writing to memory and initializing the pointer:
currentAddress = startAddress; //initialize the currentaddress pointer to the beginning of page A
*currentAddress = variable; //write data to the current address in ram
In the debugger it says that *currentAddress = undefined. Any ideas why I can't write to paged RAM?