11_registers_and_counters - Registers A single FF stores one bit A group of n FFs stores n-bits and is called an n-bit register Illustration When

11_registers_and_counters - Registers A single FF stores...

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ECE124 Digital Circuits and Systems Page 1 Registers A single FF stores one bit A group of n FFs stores n-bits and is called an n-bit register. Illustration: When clear=0 , all flip-flop outputs are forced to zero (active low reset). When clear=1 , the rising edge of the clock (the active clock edge), results in the 4-bit input transferred to register output. D Q R D Q R D Q R D Q R clock clear I3 I2 I1 I0 A3 A2 A1 A0
ECE124 Digital Circuits and Systems Page 2
ECE124 Digital Circuits and Systems Page 3 Parallel loads (2) D Q R D Q R D Q R D Q R clock clear I3 I2 I1 I0 A3 A2 A1 A0 load When load=1 , the data inputs reach the D-input of the flip-flop. When the active clock edge arrives, the data gets transferred, or loaded , to the register output. When load=0 , the data output of each flip-flop is fed back to its D-input. When the active clock edge arrives, the data input gets transferred to the register output, but since the values are the same for all flip-flops, the register holds its current value.
ECE124 Digital Circuits and Systems Page 4 .
ECE124 Digital Circuits and Systems Page 5 Comment
ECE124 Digital Circuits and Systems Page 6
ECE124 Digital Circuits and Systems Page 7 Universal shift registers (2) 4-bit register capable of multiple operations (use multiplexers instead of AND/OR gates at FF inputs): D Q R D Q R D Q R D Q R clock clear I3 I2 I1 I0 A3 A2 A1 A0 00 01 10 11 00 01 10 11 00 01 10 11 00 01 10 11 data in (rshift) data in (lshift) c1c0