Assuming I am using the EMC for both accessing the LCD buffer and external flash, where I have my executable code stored, how will execution time be affected?

[lpcware-support]

If the LCD controller has higher priority than the other devices that use the EMC, the other devices will be delayed until they can get the EMC bus. In the case of the CPU, the CPU will stall until it can get the bus. Unless the DMA request rate is very high, the CPU stalls shouldn't impact performance too much.