How To Calculate Timing States In 8085 Microprocessor

How To Calculate Timing States In 8085 Microprocessor

CLK:-The clock is the machine clock it goes up and low.

A15-A8 :-These are the higher order address lines store only address,Here we put the higher order address.

AD7-AD0 :-These are the lower order address lines.This is a multi plexed Address/Data bus.Firstly we store lower order address in this and after that we put data in it.

ALE :- It is a positive going pulse which indicates that the bits on AD7-AD0 are address bits.This latches lower order bus and generate to seperate 8 address lines.

IO/M bar:-These are the status signals .Different signals give different results.

Opcode fetch (IO/M bar=0,S1=1,S0=1)
Memory Read (IO/M bar=0,S1=1,S0=0)
Memory Write (IO/M bar=0,S1=0,S0=1)
I/O Read (IO/M bar=1,S1=1,S0=0)
I/O Write (IO/M bar=1,S1=0,S0=1)
Interrupt Accow. (IO/M bar=1,S1=1,S0=1)

AS general rule :-
If there is 1 byte instruction we will require minimum 4T states.
If there is 2 byte instruction we will require minimum 7T states.
If there is 3 byte instruction we will require minimum 10T states.

For opcode fetch 4T states.
read 3T state.
write 3T state.

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