Generation Of Effective Virtual Address (Indirect Real-Extended Addressing) - Xerox 560 Reference Manual

Instruction in memory:
Instruction in instruction register:
Indi rect reference addresses:
Contents of indirect reference address:
Address used if bit 0
=
1:
Displacement aligned for halfword indexing:
Final effective address:
II
Ir]-o
-]]-1-]2-]-3 -]4"' ] : .... ::-6 -:-]:-]-:I-:-2-
f
]-:-2
- : 3 - 1 - : : - 4 - ~ - 5
-:-2-:-1:-8
-~9-:o--':,lo
0
Figure 9. Generation of Effective Virtual Address (Indirect Real-Extended Addressing)
These are the register formats for byte-string instructions:
Byte-string instruction:
Register R:
24 Main Memory
20-bit signed disp acement,
sign extended before use
Register Rul:
During real-extended addressing memory write protection
is invoked.
Table 1 summarizes the addressing characteristics.