sm charts

1

Digital Design using ASM Charts

ASMs have three types of building blocks: 1. state box 2. decision box 3. conditional output box

The state box.Figure 8.4

The decision box. (a) Symbol. (b) Alternate symbol.Figure 8.5

The conditional output box.Figure 8.6

ASM chart for a mod-8 binary counter.Figure 8.13

State output isstate code

ASM chart for a mod-8 binary up-down counter.

Input Icontrolsdirection

An ASM chart to illustrate state assignment.Figure 8.21

A ->A,B

B->A,C,D

C->C,D

D->E

E->A

3 state bits needed

Assign codes to each state

2

State Diagrams vs. ASM Charts

Invalid ASM block having nonunique next states.Figure 8.11

Both exits selected when

both inputs are 1

Looping. (a) Incorrect. (b) Correct.Any closed loop must contain at least one state box

Looping. (a) Incorrect. (b) Correct.Any closed loop must contain at least one state box

Linked State Machines

3

When a machine becomes large and complex is desirable to divide the machine up into several smaller machines that are linked together