Enable LCD corrupts SDRAM data?

lpcware — Wed, 15 Jun 2016 18:09:07 GMT

Content originally posted in LPCWare by tjoAG on Thu Jun 07 06:10:24 MST 2012
Hi All

I see a strange things with my platform. It makes no sense!!

The EMC is setup and I can read and write to the SDRAM. For that I have created a small SDRAM test program, that also runs various RAM tests to verify it.

If I add code enabling the LCD controller I start seeing strange things.

I have located the frame buffer in the SDRAM from address 0xA000 0000 to 0xA002 6000. This area is reserved and not used by code.
The rest of the SDRAM is used for code and is run from that.

The power up sequence after all register and GPIO are setup is:

// Power-up sequence
LPC_LCD->CTRL |= (1 << LCDEN);
millisecond_delay(100);
LPC_LCD->CTRL |= (1 << LCDPWR);
</br>

Doing this, resulting in data in the frame buffer (and else where in my SDRAM) changes every time I step through code after this??? Also seen on the display.

This is verified by using the "view memory" function in KEIL.

Removing these 3 lines, and nothing changes in the frame buffer when stepping thorugh the code!!
But of course, nothing is shown on the display

I know it sounds strange!

Thomas

topic Enable LCD corrupts SDRAM data? in LPC Microcontrollers

Enable LCD corrupts SDRAM data?