HP-41C Extended Functions - 4K module?

[Dan Grelinger]

(03-01-2018 04:50 PM)Sylvain Cote Wrote:  To my knowledge ...
The Extended Functions/Memory module contains a 4KW (10 bits word) ROM and 127 extended RAM registers (889 bytes).
Unlike the 41CX (page 3), the module uses one of the lower port address (page 8, 10, 12 or 14) for it's ROM part.
There is no code for page switching in it.

Thanks for the contribution.

However, a correction that I am aware of. The Extended Functions/Memory module contains 128 RAM registers (896 bytes) 040H through 0BFH (inclusive). One register is consumed by the operating system to keep track of what address the next module occupies in the RAM address space (either starting at 201H or 301H, depending on whether the first X Memory module was inserted into Ports 1/3 or Ports 2/4). Similarly, the Extended Memory Modules (HP82181A) have 239 registers, 238 for use by the user, and one register containing pointers to the other extended memory blocks.