+ +----- address extension (supported only on Minsk-22)
+
+
+Address extension:
+
+ In Minsk-22 mode, the address extension bits can be used to access the second
+ bank of memory in the machine. Each of the bits selects the memory bank
+ (either 0 or 1) that one of the operands operate on:
+
+ The first (high) bit selects the memory bank for operand1 (x)
+ The second (low) bit selects the memory bank for operand2 (y)
+
+ The instruction pointer always operates on bank 0. This extends to situations
+ where a (jump) instruction sets the instruction pointer to either x or y; the
+ address extension bits are effectively ignored in those cases.
+
+ Similarly, the indexing word is always read from bank 0.
+
+ In Minsk-2 mode, setting the address extension bits to anything but 0 is an
+ error in all cases.