Several days before,i have contacted the freescale fae to seek for some methods to manipulate the external dual-port ram.
We have accomplished this goal by receiving a demo code.
Our's chip of mc68hc912dg128ccpv has a 128K bytes of flash eeprom,we are not sure of whether this 128K bytes flash eeprom is read-only or read-write?
because we may have a code of 100K bytes,maybe 50K bytes of them need to operate to read and write,i think ram(0x2000-0x3FFF) is not adequate.
So i program a code below,in this code, i want to set page3,page4,page5 to be internal expended ram space to make the data can be read and write,just leave page0,page1,page2 to be internal rom to. be read only.
some code below in project.prm:
RAM = READ_WRITE 0x2000 TO 0x3FFF;
/* unbanked FLASH ROM */
FLASH_PAGEC000 = READ_ONLY 0xC000 TO 0xFEFF;
/* banked EXTERNAL FLASH RAM */
FLASH_PAGE4000 = READ_WRITE 0x4000 TO 0x7FFF; //set 4000-7FFF to be external ram
/* banked FLASH RAM */
FLASH_PPAGE3 = READ_WRITE 0x38000 TO 0x3BFFF; //set page3,4,5 to be internal ram
FLASH_PPAGE4 = READ_WRITE 0x48000 TO 0x4BFFF;
FLASH_PPAGE5 = READ_WRITE 0x58000 TO 0x5BFFF;
/* banked FLASH ROM */
FLASH_PPAGE0 = READ_ONLY 0x08000 TO 0x0BFFF; //set page0,1,2 to be internal rom
FLASH_PPAGE1 = READ_ONLY 0x18000 TO 0x1BFFF;
FLASH_PPAGE2 = READ_ONLY 0x28000 TO 0x2BFFF;
EEPROM = READ_WRITE 0x0800 TO 0x0FFF;
COPY INTO FLASH_PAGEC000/*, FLASH_PAGE4000*/; //original ram
DEFAULT_ROM INTO FLASH_PPAGE0, FLASH_PPAGE1, FLASH_PPAGE2;
DEFAULT_RAM INTO RAM;
/* set banked EXTERNAL FLASH RAM */
MY_EX_RAM_PG INTO FLASH_PAGE4000; //external ram
a part of the code in main.c:
#pragma DATA_SEG MY_EX_RAM_PG //set dataRAM array in external ram
#pragma DATA_SEG __PPAGE_SEG FLASH_PPAGE3 //set ram01 array in page3
#pragma DATA_SEG __PPAGE_SEG FLASH_PPAGE4 //set ram02 array in page4
#pragma DATA_SEG __PPAGE_SEG FLASH_PPAGE5 //set ram03 array in page5
#pragma DATA_SEG DEFAULT
some code has been omit.......
RAM01 = 0x0A; //i want to use this array RAM01
compiler tell me the mistakes as follows:
Link Error : L1102: Out of allocation space in segment RAM at address 0x2101
Link Error : Link failed
i have set the option :PPAGE is used for banking.
so i do not know how to set the internal expended ram,and rom. how to use anything in page3 or page2?how to use RAM02[ xx] array?
we can see the code in demo code:
pragma CONST_SEG __PPAGE_SEG MY_EX_RAM_PG0A
how to visit datarom_02? read-only?