```
```

2 bit counter

A = lsb ; B = msb

up count:

B A

0 0

0 1

1 0

1 1

0 0

down count:

B A

1 1

1 0

0 1

0 0

1 1

where the functs:

/A := A ;always toggle

/B := /B * /A * UP ; hold on up

+ /B * A * /UP ; hold on down

+ B * A * UP ; toggle up

+ B * /A * /UP ; toggle down

i can get how the A comes, but i still did not get how the /B funct becomes like that. actually i had got the answer by guessing. but, i felt i did something that unsure, not an "official" way to solve the equations. could anyone help me out to explain, where the B equ comes from?

thanks a lot

Both A and B are driven by feedbacks.

Since the equations are registered, a change only happens on a clock edge.

From the equations alone, you don't know the initial conditions of either a or b. That depends on the device.

Since the equations are registered, a change only happens on a clock edge.

From the equations alone, you don't know the initial conditions of either a or b. That depends on the device.

i mean how can i get the answer for /B equation.