MC9S08QE8 RAM

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MC9S08QE8 RAM

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juliancox
Contributor V

I amusing a S08QE8 CPU and I don't have enough RAM.

I am using the ProcessorExpert.prm statement:-

FLASH_TO_RAM =  READ_ONLY    0xF000 TO 0xF06F RELOCATE_TO 0x01F0;

but there is no unused ram at this address. According to the users manual Direct page registers are from 0x0000 to 0x005F and RAM from 0x0060 to 0x025F. In the ProcessorExpert.prm file Z_RAM is defined as 0x0060 to 0x007F and when I examine this memory area it appears to be unused. However, if I change the RELOCATE address to 0x0060 the program will not load. What is Z_RAM (i guess that it is zero page RAM) and how can I use it to solve my space problem?

 

 

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vicentegomez
NXP TechSupport
NXP TechSupport

Hi

Variables allocated on the direct page (between 0 and 0x7F) are accessed using the direct addressing mode. This kind of accessing is faster than extended addressing mode. So we can put some variables in this Z_RAM, thus we can access them faster.
You did not use this segment in your project. So we can save some memory addresses from Z_RAM to RAM.
On how to use Z_RAM, please consult {C:\Freescale\CW MCU v11.1\MCU\Help\PDF

__SHORT_SEG Segments.

 

You just need to change the ProcessorExpert.prm file for instance

Z_RAM = READ_WRITE 0x0060 TO 0x0065;
RAM = READ_WRITE 0x0066 TO 0x025F;

 

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