Accessing external memory in MC9S12NE64

shyam_adsul — Wed, 03 Jan 2007 21:47:17 GMT

Hi all,

I am working on MC9S12NE64 microcontroller.

I am using it in Normal Expanded Wide mode where in my external memory starts from 0x208000.

Corresponding PPAGE register value is 20. EMK bit in mode register is set.

I am booting as Normal single chip mode and then putting my processor in Normal Expanded Wide.

For this I added startup code as below:

************************************************************************

LDD #$0CE2
STD $0A

LDAA #$01
STAA $13

LDAA #$00
STAA $0E

************************************************************************

The way I am trying to write on external memory is as follow.

************************************************************************

unsigned int *far p=(unsigned int *far)(0x208000);

while(1)

{

*p=0x5555;

}

************************************************************************

I am expecting PPAGE value should reflect on XADD19 to XADD14. When I probed XADD19 pin on oscilloscope, I observed that it is continuously low, which is not correct. Instead I am getting activity on XADD18.

Please let me know if I am missing anything.

Thanks and Regards,

Shyam

Re: Accessing external memory in MC9S12NE64

DrSeuss — Thu, 04 Jan 2007 21:54:51 GMT

This is normal. Please see page 16 of AN2287, on the freescale website.

Basically the PPAGE value is shifted on XAD lines to create a linear address for the memory.

topic Accessing external memory in MC9S12NE64 in S12 / MagniV Microcontrollers

Accessing external memory in MC9S12NE64

Re: Accessing external memory in MC9S12NE64