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Some preliminary consideration of the Bit Management (test/set/reset)
unit. This one can reset any specified bit to "0", set it to "1"
or test its state.
The load/store unit is responsible for generating the required
memory address. Depending on the state of instruction bits 10,
11 and 12, this address is one of
o 0: an absolute address specified in the 2nd instruction field (40-bit instruction)
o 1: Stack Pointer: The address specified by the stack pointer is used
o 2: Index Register + displacement specified in the instruction
When the stack pointer is used, it is subsequently incremented
or decremented automatically by this unit, corresponding to
a stack "POP" or "PUSH".
