hello,

we have used this 89c55,89c55wd with external SRAM and FRAM which works same as of 89c52. In fact we replaced the 89c52 with 89c55 just to get the extra code memory.

for which perpose you are using external RAM?
Is it as a scratch pad ?
which compiler you r using ? some compiler allows to use external memory in the same way as internal RAM.

have a fun,
JAY