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TTL-series counters (7490,7492,7493)

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Circuit Description

This applet demonstrates the 749x counters from the TTL-series or HC-series of (small-scale) integrated circuits.

The most popular counter ICs from the 74xx series are the following, each of which is included in the applet:

  • 7490, a 1:10 counter which can be split into 1:2 and 1:5
  • 7492, a 1:12 counter which can be split into 1:2 and 1:6
  • 7493, a 1:16 counter which can be split into 1:2 and 1:8
All three ICs are based on JK flipflops and feature asynchronous reset inputs. The first counter stage uses separate input and output pins, and can be used as a standalone 1:2 counter stage. The remaing three stages are connected internally, so that the carry and feedback paths are not accessible from the outside. To connect both stages, the A output of the first stage is connected to the CB input of the next stage(s).

Note the curious 0-1-2-3-4-5-8-9-a-b-c-d count-sequence of the 7492.

Exercise: Describe how to realize the missing counters (e.g., 1:3, 1:7, 1:9) with the 749x integrated circuits.

Print version | Run this demo in the Hades editor (via Java WebStart)
Usage | FAQ | About | License | Feedback | Tutorial (PDF) | Referenzkarte (PDF, in German)
Impressum http://tams-www.informatik.uni-hamburg.de/applets/hades/webdemos/30-counters/60-ttl/749x.html