HI Mr.Kef,
Thanks very much for your reply. I think i will use P&E to enable the Serial Monitor for my project.
And one more thing,,here i face some pecurial problem, please have a look at it..
In my project, as the default Memory Re-map in the _Startup() is blocking by the _HCS12_SERIALMON,
I modified the default Reset Vector (i.e Vector at 0xFFFE) to my own ISR called _EntryPoint() in which I re-map the memory for RAM & EEPROM and then call the _Startup() function as below.
interrupt void _EntryPoint(void)
{
*(uint8_t *)0x0011 = 0x00;
INITRM = 0x31; /* RAM size : 4K , range : 0x3000 ~ 0x3FFF */
INITEE = 0x09;
MISC = 0x01;
__asm jmp _Startup;
}
{
*(uint8_t *)0x0011 = 0x00;
INITRM = 0x31; /* RAM size : 4K , range : 0x3000 ~ 0x3FFF */
INITEE = 0x09;
MISC = 0x01;
__asm jmp _Startup;
}
and configured my .prm file to have RAM size from 0x3000 to 0x3FFF.
So, untill now there is no problem as I am using MC9S12D64. But recently i have changed my MCU from MC9S12D64 to MC9S12DG128. As you know, MC9S12DG128 has 8Kbyte of RAM which can be mappable to any 8Kbytes of total memory (I.e. from 0x0000 to 0xFFFF).
As MCU is changed and the RAM memory of new MCU is 8Kbyte, i have to change the INITRM value in my isr _EntryPoint() to 0x21 or 0x20 and i have to configure my .prm file to have RAM memory from 0x2000 to 0x3FFF.
But here i did a mistake, i changed my .prm file to have RAM memory from 0x2000 to 0x3FFF in the SECTIONS. But i forget to change the value that is assinged to INITRM register in my ISR (_EntryPoint()). It is same as previous value, i.e. INITRM = 0x31.That means, MCU tires to assign the RAM memory from 0x3000 to 0x4FFF(since RAMHAL bit dont have any effect for this MCU), which can not be acceptable for MC9S12DG128 as it has 8Kbyte RAM memory.
So, in this situation we generally expect the system should go to some malfunction or might expect to halt with illegal bp. But, there is no such of situation here. My system is working very fine even though i wrote 0x31 to INITRM register for MC9S12DG128 which is very very strange to me..
how is it possible..? How my system is not getting halted ..?? What might be the possible reasons..?? 
I feel there is something that is restricting my RAM memory going beyong 0x3FFF, but i couldn't figure out what it is..
INITRM = 0x31; /* RAM size : 4K , range : 0x3000 ~ 0x3FFF */...and configured my .prm file to have RAM size from 0x3000 to 0x3FFF.So, untill now there is no problem as I am using MC9S12D64. But recently i have changed my MCU from MC9S12D64 to MC9S12DG128. As you know, MC9S12DG128 has 8Kbyte of RAM which can be mappable to any 8Kbytes of total memory (I.e. from 0x0000 to 0xFFFF).
Not to any 8K, but to any 8K boundary. That means 8K RAM block can be mapped to 0-1FFF, 2000-3FFF, 4000-5FFF, etc. It can't be mapped for example to 3000-4FFF.
As MCU is changed and the RAM memory of new MCU is 8Kbyte, i have to change the INITRM value in my isr _EntryPoint() to 0x21 or 0x20 and i have to configure my .prm file to have RAM memory from 0x2000 to 0x3FFF.
Not really. If what you have in D64, 4k of RAM and 64k of flash is enough for you, but you want to be able to run the same compiled binary in D128 and in D256, then you should use INITRM=0x39 and use *.prm that is valid for smallest part, your code can run in.
INITRM=0x39 remaps D64 RAM to 0x3000-0x3FFF, D128 RAM to 0x2000-0x3FFF, 12k RAM block to 0x1000-0x3FFF etc. I mentioned that before.
But here i did a mistake, i changed my .prm file to have RAM memory from 0x2000 to 0x3FFF in the SECTIONS. But i forget to change the value that is assinged to INITRM register in my ISR (_EntryPoint()). It is same as previous value, i.e. INITRM = 0x31.That means, MCU tires to assign the RAM memory from 0x3000 to 0x4FFF(since RAMHAL bit dont have any effect for this MCU), which can not be acceptable for MC9S12DG128 as it has 8Kbyte RAM memory.
Again, RAMHAL is irrelevant for 2, 4, 8 and 16k RAM blocks. INITRM=31 remaps 8k of D128 RAM to 0x2000-0x3FFF.
So, in this situation we generally expect the system should go to some malfunction or might expect to halt with illegal bp. But, there is no such of situation here. My system is working very fine even though i wrote 0x31 to INITRM register for MC9S12DG128 which is very very strange to me..
:smileyhappy:. You did set in prm, that your RAM is at 0x2000-0x3FFF. And INITRM=0x31 perfectly matches that. On D128 INITRM=0x20, 0x21, 0x22..0x3F do the same, remap D128 8K RAM block to 0x2000-0x3FFF.
Regards
Yes Mr.Kef.,,
Exaclty,.. I got cleared with this issue completly 
Some of the INITRM bits will be ignored according to the RAM memory size of the derivative....
With your previous post, I got cleared with this and
The Memory Mapping Control Module (MMC) datasheet of MC9SDG128 also tells that which bits are relevant for INITRM register according to derivative... ( Table 3-3, Page No.17)
Thank you very much agian..this is such a useful information for me.. 
