\n| S<\/td>\n | Z<\/td>\n | <\/td>\n | AC<\/td>\n | <\/td>\n | P<\/td>\n | <\/td>\n | CY<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n The bit position of the flip flop in flag register is above;
\n1. Sign(S)- If D7 of the result is 1 then sign flag is set otherwise reset. As we know that a number on the D7 always decides the sign of the number.
\nif D7 is 1: the number is negative.
\nif D7 is 0: the number is positive.<\/p>\n 2. Zeros (Z)-If the result stored in an accumulator is zero then this flip flop is set otherwise it is reset.<\/p>\n 3. Auxiliary carry (AC)-If any carry goes from D3 to D4 in the output then it is set otherwise it is reset.<\/p>\n 4. Parity (P)-If the no of 1’s is even in the output stored in the accumulator then it is set otherwise it is reset for the odd.<\/p>\n 5. Carry(C)-If the result stored in an accumulator generates a carry in its final output then it is set otherwise it is reset. The carry flag also serves as a borrow flag for subtraction<\/p>\n \n- Instruction register and decoder<\/strong><\/li>\n<\/ul>\n
It is an 8-bit register. When an instruction is fetched from memory then it is stored in the Instruction register. Instruction decoder decodes the information present in the Instruction register.<\/p>\n \n- Timing and control unit<\/strong><\/li>\n<\/ul>\n
It provides timing and control signals to the microprocessor to perform operations. Following are the timing and control signals, which control external and internal circuits \u2212<\/p>\n \n- Control Signals: READY, RD\u2019, WR\u2019, ALE<\/li>\n
- Status Signals: S0, S1, IO\/M\u2019<\/li>\n
- DMA Signals: HOLD, HLDA<\/li>\n
- RESET Signals: RESET IN, RESET OUT<\/li>\n<\/ol>\n
\n- Interrupt control<\/strong><\/li>\n<\/ul>\n
As the name suggests it controls the interrupts during a process. When a microprocessor is executing the main program and whenever an interrupt occurs, the microprocessor shifts the control from the main program to process the incoming request. After the request is completed, the control goes back to the main program.<\/p>\n There are 5 interrupt signals in 8085 microprocessor: INTR, RST 7.5, RST 6.5, RST 5.5, TRAP.<\/p>\n \n- Serial Input\/output control<\/strong><\/li>\n<\/ul>\n
It controls the serial data communication by using these two instructions: SID (Serial input data) and SOD (Serial output data).<\/p>\n \n- Address buffer and address-data buffer<\/strong><\/li>\n<\/ul>\n
The content stored in the stack pointer and program counter is loaded into the address buffer and address-data buffer to communicate with the CPU. The memory and I\/O chips are connected to these buses; the CPU can exchange the desired data with the memory and I\/O chips.<\/p>\n \n- Address bus and data bus<\/strong><\/li>\n<\/ul>\n
The data bus carries the data to be stored. It is bidirectional, whereas the address bus carries the location to where it should be stored and it is unidirectional. It is used to transfer the data & Address I\/O devices.<\/p>\n FEATURES OF 8085 MICROPROCESSOR:-\u00a0<\/strong><\/h3>\n\n- Intel 8085 is an 8-bit, N-channel Metal Oxide Semiconductor (NMOS) microprocessor<\/li>\n
- It is a 40 pin IC package fabricated on a single Large Scale Integration (LSI) chip<\/li>\n
- The Intel 8085 uses a single +5V DC supply for its operation<\/li>\n
- Its clock speed is about 3MHz<\/li>\n
- It provides 16 address lines so it can access 2^16 = 64 KB of \u00a0\u00a0memory<\/li>\n
- Accumulator based<\/li>\n
- It has 80 basic instructions, 246 op-codes, and 5 addressing modes.<\/li>\n
- It contains 6200 transistors approx.<\/li>\n
- Its dimensions are 164mm x 222 mm<\/li>\n<\/ul>\n
INSTRUCTIONS AND DATA FORMAT OF 8085 MICROPROCESSOR <\/strong><\/h3>\nA microcomputer performs a task by reading and executing the set of instructions written in its memory. This set of instructions, written in a sequence is called Program.<\/strong><\/p>\nIt is a group of bits<\/strong> that instruct the computer to perform a specific operation.<\/p>\nAn\u00a0instruction<\/strong> is a command to the microprocessor to perform a given task on a specified date.<\/p>\nEach instruction has two parts: one is the task to be performed, called the operation code (op-code), and the second is the data to be operated on, called the operand.<\/strong><\/p>\n8085 has 80 basic instructions, 246 op-codes.<\/strong><\/p>\n\n\n\nOpcode <\/strong><\/td>\n| Address\/operands<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Fig: Instructions format<\/strong><\/p>\nOp Code<\/strong>= <\/strong>Operation to be performed<\/p>\nAddress<\/strong> = <\/strong>address of operand on memory<\/p>\nEg:\u00a0 A + B <\/strong><\/p>\n Operands = A B<\/strong><\/p>\nOpcode = +<\/strong><\/p>\nTYPES OF INSTRUCTION FORMATS<\/u><\/strong><\/p>\nThe 8085A instruction set consists of one, two and three-byte instructions. The first byte is always the opcode; in two-byte instructions, the second byte is usually data; in three-byte instructions the last two bytes present address or 16-bit data.<\/p>\n \n- One Byte Instruction Formats:<\/strong><\/li>\n<\/ol>\n
\n- Generally, the op-code & operand are 8-bit or 1 byte.<\/li>\n
- Specifies the operation which has to be performed or who going to do that operation.<\/li>\n
- Generally, only one byte of a memory location is required.<\/li>\n
- Format: Op-code, <\/strong>In this only op-code is present<\/li>\n<\/ul>\n
Eg: MOV B,\u00a0 C;\u00a0 Move Data; copy the content of C register to B register without modifying the content of the source register.<\/strong><\/p>\n\n- Two Byte Instruction Formats:<\/strong><\/li>\n<\/ol>\n
| | |
![\"ARCHITECTURE](\"https:\/\/bcisnotes.com\/thirdsemester\/wp-content\/uploads\/2019\/01\/8085_architeccher.png\")
<\/p>\n![\"INTEL](\"https:\/\/bcisnotes.com\/thirdsemester\/wp-content\/uploads\/2019\/01\/370px-ABasicComputer.gif\")
<\/p>\n