... with no external code memory access (e.g. LPC9xx, the SiLabs, the 20-pin AT89Cx051-s).

For the others, the behaviour of MOVC^* in all combinations (MOVC fetched from internal/external code memory x accessing internal/external code memory x /EA) is dependent mostly on the lockbit settings, and is (should be) described in the respective datasheet/user manual of the given derivative. Customarily, above a certain security level (determined by the combination of lockbits), the /EA pin is sampled and latched at reset (note that some datasheets say even something this: "The latched value of /EA must match the current state of the /EA pin, otherwise the behaviour of chip is undefined" - while others claim, "changing /EA after being latched has no effect").

For a nice example, see table 9-2 at page 62 of the SST's '516RDx datasheet. Most of the datasheets don't have such a table, but you should be able to construct one from the textual description of the lockbits.

JW


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* the basic MOVC function is fully described in the "bible", including that /PSEN is pulsed when MOVC accesses external memory - I hope it is not necessary to point out the exact page number in the bible, searching for "MOVC" will yield it quickly enough.