Logic diagram of 8085
Fig: 8085 flag register Flags are flip-flops which are used to indicate the status of the accumulator and other register after the completion of operation. These flip-flops are set or reset according
to the data condition of the result in the accumulator and other registers. Logical instructions in 8085 microprocessor. Logical instructions are the instructions which perform basic logical operations such as AND, OR, etc. In 8085 microprocessor, the
destination operand is always the accumulator. Here logical operation works on a bitwise level. Following is the table showing the list of logical instructions: In the table, Therefore, it is necessary to increase driving capacity of the 8085 buses. Bus drivers, buffers are used to increase the driving capacity of the buses. Unidirectional Buffers : As we know, the address bus is unidirectional, 8-bit unidirectional buffer, 74LS244 is used to buffer higher address bus. The Fig. 4.10
shows the logic diagram of 74LS244. 8085 is a 40 pin IC, Pin Diagram and Pin description of 8085. 8085 is a 40 pin IC, The signals from the pins can be grouped as follows. 1. Power supply and clock signals; 2. Address bus; 3. Data bus; 4. Control and status signals; 5. Interrupts and externally initiated signals Author:
Shankar After receiving sixteen bit address for CALL, 8085 pushes the contents of the PC onto the stack and branches the program control to the subroutine whose address is received from the external logic. Example : The Fig. 5.4 shows the diagram of external logic that gives the RST 7 instruction opcode on interrupt acknowledge. Logical Instructions Of 8085 Microprocessor Logical Instructions. CMP R (Compare register with accumulator). A – R. CMP M (Compare memory with accumulator). A – (M). CPI 8 - bit data (Compare. To execute programs, the microprocessor reads instructions and data from memory Fig
(a) - Pin Diagram of 8085 & Fig(b) - logical schematic of Pin diagram. The following diagram shows the location of the ALU in the 8085. The ALU is 8 bits wide, with the high-order bit on the left. The register file is the large block below the ALU. The registers are 16 bits wide, made up of pairs of 8-bit registers. Surprisingly, the register file has the high-order bit on the right, the opposite order from the ALU.