S12 / MagniV MicrocontrollersのトピックRe: Problems writing to paged ram on an HC12

Problems writing to paged ram on an HC12

CJTill — Tue, 23 Jun 2009 00:23:28 GMT

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:

XGATE_STRING_RAM,

XGATE_CONST_RAM,

XGATE_CODE_RAM,

XGATE_DATA

INTO RAM_F8;

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?

Re: Problems writing to paged ram on an HC12

kef — Tue, 23 Jun 2009 03:40:39 GMT

I think the problem is that pointers to far data use global addressing GPAGE+16bit G-page offset. And you specified your addresses using RPAGE + 16bit cpu local address. For example 0xFA1000 is RPAGE=0xFA, and CPU local address 0x1000. I don't know how familiar you are with this, but try converting RPAGE RAM addresses to GPAGE RAM addresses, like this

#define RPAGE2GPAGE(x) ((x&0xFFF) | ((x>>4)&0xFF000))

INT16U *__far startAddress = (INT16U*__far) RPAGE2GPAGE(0xFA1000);
INT16U *__far endAddress = (INT16U*__far) RPAGE2GPAGE(0xFC1FFF);

Re: Problems writing to paged ram on an HC12

CJTill — Tue, 23 Jun 2009 04:24:04 GMT

Ok, thanks I see what I need to do now. I will need to change the RPAGE register to write to the correct location.