César,

Your RAM is probably not located in the Code address map but in the Data map.

You mentioned a monitor, if it "downloads" the RAM while it is in Data space it should provide a method (probably with an intervening RESET) for "swiching" the RAM into the code address map.

If the above is true the next question would be "where". If it switches the RAM into the 0-1FFFH space usually occupied by your ROM, then your interrupt vectors would call code within the 0-1FFFH address range.

regards,
p