CMPUT329 - Fall 2003

TopicJ: Counters

José Nelson Amaral

Reading Material

Section 8.5 of Wakerly.

Shift Registers

A shift register is an n-bit register that can shift its stored data by one

bit position at each clock tick

A serial input (SERIN) specifies a new bit to be shifted in.

A serial output (SEROUT) has the value of the bit that is shifted out.

In a serial-in serial-out register only one bit is out at any clock cycle.

In a serial-in parallel-out register all stored bits are out at every clock cycle.

Shift Registers

serial-in, serial-out

serial-in, parallel-out

Shift Register
parallel-in, serial-out

MSI Shift Registers

Bidirectional

Shift Register
parallel-in, parallel-out

Quiz

Design a function table for a 4-bit shift register that at any clock cycle

can perform one of the four functions:

Hold: keep the same value that it had in the previous cycle

Shift right: shift the values to the right, and shift in the value of an RIN input

Shift left: shift the values to the left, and shift in the value of an LIN input

Load: Load the values of inputs A, B, C, D, into flip-flops QA, QB, QC, QD.

If you were to specify this shift register as a finite state machine, how

many states your machine would have?

74x194: 4-bit
Universal Shift Register

FSM for the 74x194

0000

0001

0010

0011

0100

0101

0111

0110

1000

1001

1010

1100

1011

1110

1101

1111

SL & LIN=1+ Load & ABCD=0001

SR & RIN=1+ Load & ABCD=1000

Hold + Load & ABCD=0000

74x194: 4-bit

Universal Shift

Register

74x194: 4-bit

Universal Shift

Register

74x299: 8-bit Universal
Shift Register

The 74x299 is an 8-bit version of the 74x194. It implements

bidirectional three-state lines for input and output to save pins.

74x299: 8-bit

Universal Shift

Register

Serial/Parallel Conversions

SYNC is a reference signal that indicates the beginning of a byte or word.

Parallel-to-serial conversion frame

CMPUT329 - Fall 2000

CMPUT329

Jose Nelson Amaral

1998-02-10T08:49:30

Trial User