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how to draw timing diagram?discuss the various steps
You first need to understand the machine cycles of 8085
The status signals are as follows
IO/M(bar) :--- 1 IO 0 Memory
S1 | S0 | Process
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0 | 0 | Halt
0 | 1 | Write
1 | 0 | Read
1 | 1 | Opcode fetch
1)Opcode fetch ( Compulsory Machine cycle)
This cycle requires 4 T-states.
1st T state ALE is high and lower byte of address from PC(Program Counter) is placed on the multiplexed data/address bus.
In the second T-state, after checking the status of READY pin, RD(bar) goes low the opcode is placed on the data bus, This state continues in the 3rd T-State.
The fourth T-state is used by the uP to decode the instruction and to generate the relevant control signals. The state of the address bus is unspecified( This T-state is used by some DMA controllers to transfer data in hidden/transperant mode)
IO/M_ = 0 S1=1 S0=1
2)Memory read(for 1 byte)
Three T states, similar to the first 3 T states of opcode fetch( as first 3 states of opcode fetch is effectively memory read)
IO/M_ 0 S1 = 1 S0 = 0
3) Memory Write(for 1 byte)
Similar to Write but instead of RD bar WR bar is used. Also the data stays on the bus a little longer than READ*.
IO/M_ 0 S1 = 0 S0 = 1
4) & 5) IO write and read
Simlar to the above two, only IO/M_ = 1
These are the basic machine cycles you will require to draw timing diagrams for most instructions. There are additional cycles such as INTA bar and Bus idle. If anyone requires diagrams for these cycles, message me and i will explain them later.
Also some instructions like CALL require 6 T-state Opcode fetch. For this you can draw the 4 T state Opcode fetch but 4th T state extended to the fifth and sixth T state.
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Now, to draw the timing diagram for any instruction you need to understand what exactly the instruction does. I will explain a few. If you need a specific instruction, msg me.
A) MOV A,B
Draw only opcode fetch as no further memory acces is required as operands specified in registers only
B) MVI A,32H
Draw opcode fetch and memory read as operand(1 byte) has to be fetched from memory
C) LXI H, 2000H
Draw Opcode Fetch and two memory Reads as two bytes, 00H and 20H, (lower byte fetched first) have to be read from memory.
D) STA 2000H
This instruction stores the value of accumulator(8 bit) at the location specified.
Opcode fetch + Memory read * 2 (byte address) + Memory write * 1(1 byte)
i.e 13 T-states 4+3+3+3
During the memory write the address bus contains the address fetched by the memory read cycle earlier
E) CALL addresss(can be specifed in terms of a label)
During a call instruction the uP pushes the current value of program counter(16 bit ie 2 byte) to the stack and then copies the new value from the memory(specified in the instruction)
6 T state Opcode fetch
+ Memory write * 2 (PC pushed to stack)
+ Memory read * 2 (New value of PC fetched from memory)
ie 6 + 3 + 3 + 3 + 3 = 18 T-states
Note that during the memory write cycle the address bus contains the address of the top of the stack(Stack Pointer)
F)JMP 16-bit address
3 Cycles as Follows
4 T-State Opcode Fetch
+ 2 * Memory Read ( 16 bit = 2 bytes)
ie 4 + 3 + 3 = 10 T-states.
Note that separate cycle is not required for loading the address into the PC as PC is a register.
What else can I help you with?
How does the 8085 microprocessor instruction register work?
stores next instructions
What is a 8085 microprocessor?
The 8085 microprocessor is an 8-bit microprocessor introduced by Intel in 1976. It is a popular microprocessor used in many early computer systems and embedded devices. The 8085 has a 16-bit address bus and an 8-bit data bus, with a clock speed ranging from 2 to 3 MHz. It has a total of 74 instructions in its instruction set architecture.
How does a microprocessor know whether the next byte is an instruction or data?
A microprocessor know whether the next byte is an instruction or data because the microprocessor knows for what it is looking. The bus, on the other hand, for an 8085 based system, knows an opcode from data by looking at S0 and S1 when IO/M- is low. If both are high, it is an opcode, otherwise it is data.
Where can you download book on microprocessor 8085?
mnsingh536@gmail.com
How many location can be accessed by 8085 microprocessor?
The 8085 microprocessor can access 65536 (2^16) locations in memory, and 256 (2^8) locations in I/O space.
How do you draw timing diagram for 8085 microprocessor instruction?
Refer http://wiki.answers.com/Q/How_to_draw_timing_diagram_for_8085_microprocessor_instruction
How do you draw timing diagram for 8085 instruction LHLD 5000H?
There is an example of a LHLD 5000H diagram on this website: atelier-drachenhaus.de/timing-diagram-8085. This will provide an idea of how to draw the diagram.
How many instruction are there in 8085 mp?
There are 74 instructions in the 8085 microprocessor.
What is timing and control unit in 8085 microprocessor?
timing
How does the 8085 microprocessor instruction register work?
stores next instructions
What is the function of control bus in references to 8085 microprocessor?
It provides timing signals.
Why is the jump instruction jmp of 8085 microprocessor given the immediate addressing mode?
because the operand is available in the instruction itself
Why the name 8085 Why the name 8085 for microprocessor?
8085 is a microprocessor designed by Intel
What is the purpose of the RRC instruction in 8085 microprocessor?
We can implement "Divided by '2' " operation by using RRC.
What Timing diagram Intel 8085 out instruction?
The OUT instruction on the 8085 uses 10 T cycles, 3 for opcode fetch, 1 for opcode decode, 3 for port address fetch, and 3 for port data store. Any wait states encountered are above and beyond that.
How many bytes are there for jump instruction in 8085?
There are 74 instructions in the 8085 microprocessor.
What are various instruction formats in 8085 microprocessor?
An instruction is a command for any given task. There are two parts to each instruction; one giving the command and two the operand.
