Service manual

STP 11-25R13-SM-TG
Q - 29
Figure Q-26. R-S Flip-Flop with State Indicator Outputs
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(14) The outputs would still be Q = 0 and Q = 1 in the RESET state. The truth table would be as
shown in Table Q-17.
Table Q-17. Truth Table
(15) R-S FFs are generally used in situations where a memory function is required which is not
synchronized with the rest of the sequential circuits. As an example, you could tell a piece of
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equipment to move up or .down by assigning Q and Q to up and down and then supply the correct inputs
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for the desired result. The example of a R-S FF, the 74279 IC chip in Figure Q-27 is actually an R-S FF.
Figure Q-27. 74279 IC Chip
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S S R R Q Q
1 0 1 0 0 1
0 1 1 0 1 0
1 0 0 1 0 1
0 1 0 1 Indeterminate state