EE101Lecture19

EE101Lecture19 - Introduction to Digital Logic Lecture 19:...

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© Mark Redekopp, All rights reserved Introduction to Digital Logic Lecture 19: Flip-Flops
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© Mark Redekopp, All rights reserved Flip-Flops vs. Latches Flip-Flops Edge-Sensitive Outputs change only on the positive OR negative edges Latches • Level Sensitive • Outputs can change anytime Clock = 1
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© Mark Redekopp, All rights reserved Master-Slave D-FF • One way to build a D-FF is to take 2 D-Latches and chain them together • Let the clock go directly to one D-FF but be inverted into the other These are latches NOT FF’s…together they form a D-FF The Master Latch gets the clock directly, the Slave gets the inverse of the clock D C Q Clock Q Q D C Q Q Q D Master Slave
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© Mark Redekopp, All rights reserved Master-Slave D-FF • First latch is referred to as master and second is referred to as slave because the input to the slave is the output of the master • The slave can only pass what the master “gives” it Q Master = D Slave D C Q Clock Q Q D C Q Q Q D Master Slave
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© Mark Redekopp, All rights reserved Master-Slave D-FF • Important: – When Clock = 0 => • Master = Hold mode, Slave = Transparent – When Clock = 1 => • Master = Transparent, Slave = Hold Mode C = 0: Hold Transp. C = 1: Transp. Hold D C Q Clock Q Q D C Q Q Q D Master Slave
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© Mark Redekopp, All rights reserved CLK D Q Master Q Slave Master-Slave D-FF CLK = 0: Master Holds, Slave Passes Q Master 01 H o l d T r a n s p . 0 D C Q Clock Q Q D C Q Q Q D Master Slave
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© Mark Redekopp, All rights reserved CLK D Q Master Q Slave Master-Slave D-FF CLK = 1: Master Passes D, Slave remembers its last value, 0 10 T r a n s p . H o l d 1 D C Q Clock Q Q D C Q Q Q D Master Slave
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© Mark Redekopp, All rights reserved CLK D Q Master Q Slave Master-Slave D-FF CLK = 0: Master remembers the last value,1 Slave Passes Q Master 01 H o l d T r a n s p . 0
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This note was uploaded on 02/27/2008 for the course EE 101 taught by Professor Redekopp during the Fall '06 term at USC.

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EE101Lecture19 - Introduction to Digital Logic Lecture 19:...

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