Page 132 - Handout Digital Electronics
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17.3 synchronous reversible counters
In practice the up and down counters are combined into one chip to produce a reversible counter that is a
counter which can count and down. The reversible counters are more popular than single up or down
counters.
Figure 60: Reversible counter circuit diagram
The diagram above is a simple 3-bit Up/Down synchronous binary counter implemented on JK flip flops
which operate as toggle or T flip flops. The maximum count is 111. The counter counts in sequence
1,2,3,4,5,6,7 or in reverse sequencing. This type of counter is bidirectional, and it can be made to change
direction at any point in the counting sequence. The Up or Down input control line determines the
direction of the count (see timing diagram figure 61).
Figure 61: 3-bit reversible synchronous binary counter
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