, it decodes the instruction and realizes it needs a 16-bit address.
: The PC places the address on the bus; ALE latches it. The processor fetches 2Bh . In T4cap T sub 4 Timing Diagram Of Lhld Instruction In 8085
: The processor reads the two-byte address from the memory locations immediately following the opcode. , it decodes the instruction and realizes it
The (Load H and L registers direct) instruction in the 8085 microprocessor is a 3-byte instruction that loads the contents of a specific 16-bit memory address into the H-L register pair . It is one of the most complex instructions in terms of timing, requiring 5 machine cycles and 16 T-states to complete. 1. Instruction Overview Opcode : 2Bh (for LHLD) In T4cap T sub 4 : The processor
: The processor places the 16-bit address it just "learned" onto the address bus. It reads the byte at that location and stores it in the L register .
) : 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
Increments the address by 1 and reads data into the . 3. Signal Behavior in the Timing Diagram