CrazyEngineers Archive
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@shruti palod • 13 Oct, 2009
Hi friends

Can anyone tell me that why there are 18 T-states
in the call instructions of an 8085 microprocessor

@Harshad Italiya • 14 Oct, 2009 If you know that how CALL instruction functions then its very simple to calculate T states

Assume at Memory Location 2000H instruction CALL 3000H is written

During a call instruction the uP pushes the current value of program counter(16 bit ie 2 byte | Here it is 2000H) to the stack and then copies the new value from the memory(specified in the instruction | Here 3000H)

So now
6 T state Opcode fetch

+ Memory write * 2 (PC pushed to stack) ( 3+3 )

+ Memory read * 2 (New value of PC fetched from memory) ( 3+3 )

ie 6 + 3 + 3 + 3 + 3 = 18 T-states.
@shruti palod • 22 Oct, 2009 Re: thanks for the reply

thanks for the reply
It increased my knowledge about
call instructions.
@Harshad Italiya • 26 Oct, 2009 Re: thanks for the reply

shruti palod
thanks for the reply
It increased my knowledge about
call instructions.
You are most welcome. Looking forward to see you active on crazyengineers.
@Manan Thakar • 18 Feb, 2011 Plz, ans me that ,Why fetching of call instruction requires 6 t-states?

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