Counters
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The document discusses different types of counters used in logic design including decades counters, binary counters, up-down counters, BCD counters, and ring counters. It provides examples of synchronous and asynchronous binary counters, BCD counters with parallel load, and specialized counters like Johnson counters. Key aspects covered are how the counters work by toggling flip-flops to count in binary or BCD. Diagrams illustrate the circuitry and signal flow for different counter configurations.
Counters
- 4. Decades Counter Q3 Q2 Q1 Q0 BCD Counter 100’s Digit Q3 Q2 Q1 Q0 BCD Counter 10’s Digit Q3 Q2 Q1 Q0 BCD Counter Count (CLK) 1’s Digit 4 / 28
- 5. Synchronous Binary Counter Q3 Q2 Q1 Q0 Enable Q Q J Q J Q J Q To Next Stage J K Q K Q K Q K CLK 5 / 28
- 7. BCD Counter 0 0000 0 1 0001 0 1 0010 0 1 0011 0 1 0100 1 1 1001 1000 1 0 0111 1 0 0110 1 0101 1 0 0 0 Q3 Q2 Q1 Q0 E 7 / 28
- 8. BCD Counter 0 0000 / 0 0 1 0 0001 / 0 1 0010 / 0 0 1 0011 / 0 0 1 0100 / 0 1 1 1001 / 1 1000 / 0 1 0 0111 / 0 1 0 0110 / 0 1 0101 / 0 1 0 0 0 Q3 Q2 Q1 Q0 y E 8 / 28
- 9. Binary Counter with Parallel Load CLR LD Count Q(t+1) 0 x x 0 1 0 0 Q(t) 1 0 1 Q(t)+1 1 1 x I I3 Q3 I2 Q2 I1 Q1 I0 Q0 LD Count CLR Usually Asynchronous Clear 9 / 28
- 10. BCD Counter Example LD 0 Q3 A3 0 I2 Q2 A2 0 I1 Q1 A1 0 Count I3 I0 Q0 A0 Count CLR 1 CLK 10 / 28
- 11. Ring Counter 0001 T3 T2 T1 T0 0010 0100 1000 CLK T0 2-to-4 Decoder T1 T2 2-bit counter T3 11 / 28
- 12. Johnson Counter 0000 0001 0011 0111 1000 1100 1110 1111 Q3 Q1 Q2 Q Q D Q Q D Q0 Q Q D Q D Q CLK 12 / 28
- 13. Binary Counters • Binary Counters do exactly what it sounds like they should. They count in binary. • Binary numbers are comprised of only 0’s and 1’s. Decimal QD QC QB QA 0 1 2 3 4 5 0 0 0 0 1 1 0 0 1 1 0 0 0 1 0 1 0 1 0 0 0 0 0 0 20 March 2007 Electronic Instrumentation 13
- 14. Binary Counters are made with Flip Flops DCBA = 1100 DCBA = 1111 Each flip flop corresponds to one bit in the counter. Hence, this is a four-bit counter. 20 March 2007 Electronic Instrumentation 14
- 15. Typical Output for Binary Counter 1100 =12 DCBA = 1100 DCBA = 1111 • Note how the Q outputs form 4 bit numbers 20 March 2007 Electronic Instrumentation 15