Counters

Counter consists of an adder connected to a register. The adder is combinational and is computing the next value by incrementing the current value.

The counters have flags to control whether the adder has carry in or carry out. The COUT will be true if the current value is generating a carry. For example, an 8-bit counter will generate a COUT when the count equals 255.

Since counters contain state, they have optional CE (clock enable), RESET, and SET inputs. CLK is always included.

Create an n-bit up counter,

# UpCounter :: O:Out(Bits(n), COUT:Out(Bit)
UpCounter(n, cin=False, cout=True, incr=1, 
    has_ce=False, has_reset=False)

# DownCounter :: O:Out(Bits(n), COUT:Out(Bit)
DownCounter(n, cin=False, cout=True, decr=1, 
    has_ce=False, has_reset=False)

# UpDownCounter :: U:In(Bit), D:In(Bit), O:Out(Bits(n)), COUT:Out(Bit)
UpDownCounter(n, cout=True, has_ce=False, has_reset=False)

Generate an up-down counter. The counter is incremented by (Up-Down).

# CounterModM :: O:Out(Bits(n), COUT:Out(Bit)
counter = CounterModN(m, n, cin=False, cout=True, has_ce=False, has_reset=False)

Counter wraps around to 0 when count equals m-1.

# CounterLoad :: DATA:In(Bits(n), LOAD:In(Bit), O:Out(Bits(n), COUT:Out(Bit)
counter = CounterLoad(n, cin=False, cout=True, incr=1,
            has_ce=False, has_reset=False)