He'll learn that just because his on-chip oscillator runs at 18+ MHz and the MCU produces ALE (which I doubt he's checked, since he doesn't have the equipment) doesn't guarantee that the MCU is running properly.

I've clocked Intel 8751's at 20 MHz and seen a nice, clean ALE, yet never had 'em run at that rate. He's not yet figured out that, at 18+ MHz, the memory access time requirement won't be met by his EEPROM.

What a sensible kid would do is to build up a circuit that used a preprogrammed code ROM and and external RAM (Remember, his MCU is a preprogrammed ROM-based part, so he has to use external memory.) in order to verify that he can make everything work properly. Then he could verify that his code works, which, what he's posted won't do. Then, when he realizes that it will take longer in-circuit to program his EEPROM from the PC than it will take to reprogram an MCU with internal FLASH, and when he figures out that it's much quicker to program a code-space RAM from the PC and run the code there, then he can choose a path that makes more sense.

In the meantime, let him be ... He'll be our age before he has this thing working properly. With age comes wisdom, or so they say.

RE