Counters and Registers
421
Q A
FF0
J
K
'1'
Clock
Clk
Cl
Pr
Q A
Q B
FFB
J
K
Clk
Cl
Pr
Q B
Q C
FFC
J
K
Clk
Cl
Pr
Q C
(a)
Clock
(b)
Q A
Q B
Q C
Preset
Figure 11.6 Example 11.4.
0111, 0110, 0101, 0100, 0011, 0010, 0001 and 0000. The timing waveforms are shown in Fig.
11.8. Thus, we have a four-bit counter that counts in the reverse sequence, beginning with the
maximum count. This is a DOWN counter. This type of counter is discussed further in the subsequent
paragraphs.
421
Q A
FF0
J
K
'1'
Clock
Clk
Cl
Pr
Q A
Q B
FFB
J
K
Clk
Cl
Pr
Q B
Q C
FFC
J
K
Clk
Cl
Pr
Q C
(a)
Clock
(b)
Q A
Q B
Q C
Preset
Figure 11.6 Example 11.4.
0111, 0110, 0101, 0100, 0011, 0010, 0001 and 0000. The timing waveforms are shown in Fig.
11.8. Thus, we have a four-bit counter that counts in the reverse sequence, beginning with the
maximum count. This is a DOWN counter. This type of counter is discussed further in the subsequent
paragraphs.