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LPC4078: using 16bit bus width external SDRAM as program memory

Question asked by Otavio Borges on Jul 3, 2017
Latest reply on Jul 5, 2017 by Carsten Groen



I'm developing an application using LPC4078FBD208 and an Alliance AS4C4M16SA SDRAM IC as external memory. After bootup I'm going to load the program data from a SD card, write it on the external memory and switch CPU context to execute from the external memory.


As M4 instructions are 32bit, the SDRAM 16bit bus width represent a problem for this scenario? The memory max clock is 144MHz, therefore I'll need two clock cycles (assuming that MCU core clock will be 120MHz) to fetch an entire instruction through EMC, will I have to reduce the CPU core clock to 60MHz to work with this setup?


Thank you.