RAM & QSPI requirement for driving 800x480 TFT 24bit Parallel RGB display in MPC5645S MCU

[priyan_george]

Hi,

We are trying trying to design an instrument cluster using MPC5645S MCU. Our requirement is to drive a 7" 800 x 480 resolution 24bit parallel RGB display using MPC5645S. We have gone through some of the documents available from NXP such as AN5072, AN4444, and AN4865. But we are facing a hard time understanding the calculations in this document. It says that the speed of the RAM and QSPI is more important than the size of the memories. We have seen at some part of the document that we need to use a DDR2 RAM other than LPDDR1 ram as former has more speed. Is our understanding correct. We have gone through the reference design and there NXP has used LPDDR1.

So can anyone let us know which RAM and QSPI Memory to use to drive 7" 800 x 480 resolution 24bit parallel RGB display using MPC5645S and what size we should choose for.

[davidtosenovjan]

Hi, it is difficult question and I am afraid it is above possibilities of basic support.

To start off I want to mention that we try to avoid recommending specific devices to customers for memory and other external components. Because of the large number of choices out there it is impossible for us to have hands-on experience with all of them, and we don't want to recommend devices that we haven't used ourselves. We are at least indirectly recommending devices by including them on our EVBs and reference designs. So in most cases our best recommendation is to use the devices we have used or at least find something similar that will meet your specific needs.

However one the document explicitly says that "it is apparent that even with a fast DDR2 SDRAM, the largest panel supported with full color encoding is WVGA (800 x 480, c. 33 MHz)." what could be good hint. It is true that MPC5645SDEMO board uses LPDDR1 but it also uses smaller TFT panel. Thus I would pay your attention to DDR2 memories.

In the following link you may see excel tool (originally tailored to MPC5121E that is however using almost the same DRAM controller), showing in the bottom tabs certain DRAM devices so could possibly use it as starting point for your DRAM selection:

https://www.nxp.com/docs/en/user-guide/MPC5121EQRUGAD.xls

Regarding QSPI memory -

MPC5645S Microcontroller Reference Manual, Rev. 8, Section 35.8 shows all supported instructions codes for 4 selected vendors (Winbond / Spansion / Macronix / Numonyx chosen by QSPI_MCR[VMID]) producing (or developing) QuadSPI memories at the time of developing MPC5645S MCU (somewhere around year 2010). As I know Spansion has been acquired by Cypress, Numonyx by Micron, Winbond and Macronyx probably stays under same name.

2 x Spansion S25FL064P has been used with MPC5645SDEMO board, mentioned memory manufactures could possibly help you to choose proper device, I expect newer devices are backward compatible.

Hope it helps a bit