To visualize the diagram, consider the following behavior of the system bus during these 16 T-states:
) : Carries the most significant bits of the memory address throughout the cycle. : Acts as the lower address bus during T1cap T sub 1 Acts as the data bus during T2cap T sub 2 T3cap T sub 3 to fetch the opcode or read memory data. Control Signals ( RD¯modified cap R cap D with bar above WR¯modified cap W cap R with bar above ) : Since LHLD is a "Load" instruction, WR¯modified cap W cap R with bar above remains high (inactive). RD¯modified cap R cap D with bar above goes low during T2cap T sub 2 T3cap T sub 3 of all five cycles to enable memory reading. Status Signals ( ) : (Memory operation). For Opcode Fetch (M1): For Memory Read (M2-M5): 4. Step-by-Step Execution Timing Diagram Of Lhld Instruction In 8085
: 5 (Opcode Fetch, Memory Read, Memory Read, Memory Read, Memory Read) T-States : 2. Breakdown of Machine Cycles The timing diagram is divided into five distinct phases: Machine Cycle Description M1 Opcode Fetch 4 T-states Fetches the opcode 2Bh from memory. M2 Memory Read 3 T-states Reads the lower-byte of the 16-bit address ( M3 Memory Read 3 T-states Reads the higher-byte of the 16-bit address ( M4 Memory Read 3 T-states To visualize the diagram, consider the following behavior
(L)←[[adr]]open paren cap L close paren left arrow open bracket open bracket a d r close bracket close bracket (Content of memory address moves to L) RD¯modified cap R cap D with bar above
