external flash for the MC9S12XEP100

[zhencai]

I am using MC9S12XEP100. And I want to use the external flash to store the program when the size of my code exceed 1MB. Is it appropriate to use 28F320S5 to store the program? Anyone has the examples using the external flash for the MC9S12XEP100. I need some schematic and testing code. I appreciate your help very much.

[iggi]

Hello,

There is an application note which may be of help for this case:

AN2708 – External bus design on S12X:
http://cache.freescale.com/files/microcontrollers/doc/app_note/AN2708.pdf

Also, download the Addendum to this app note. It is attached.

Be aware that CodeWarrior and microcontroller itself do not support programming of external flash directly. External flash must be programmed either by external programmer or ctm has to develop own bootloader which will program data into flash.

Then be aware that most of 16bit flash memories do not have pins UB and LB (selection of upper byte and low byte). So, it is necessary to connect the address pins in this manner:

A1 flash ->A0 MCU

A2 flash -> A1 MCU

A3 flash -> A2 MCU

…

In this case, we can access only 16b aligned words.

Moreover you can use SPI to interface external Flash to the MCU.

Regards,
Ivan

[Eric_t]

Hi 

I know that it is an old post, but something took my attention

Moreover you can use SPI to interface external Flash to the MCU.

What does it means?

If the internal flash is not enough, we can use use SPI external Flash to save part of the firmware?

Thank you