Block diagram of a recursive difference equation representing an accumulator.

Do This:

1. Notice the value 1 is entering from the left. The output of the One-sample delay is 0 since we've just started and there was no previous value.
2. Click the Step button once. Another 1 is entering the summer. The delay has output the 1 from the previous time. The two are added and the value 2 is output from the summer.
3. Click Step a couple more times to see that this repeats.
4. Change the value of x[n] to some other value. Click Step. Do the results make sense?
5. Why is this called an accumulator?

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Oppenheim and Schafer, Discrete-Time Signal Processing ISBN 0-13-198842-5.
© 2016 Pearson Education, Inc.