Pulse counter with clock edge recovery
View Patent ↗An apparatus and a method for counting input pulses during a specific time interval are provided. A clock edge recovery output signal is produced in response to an input gating signal and a clock signal containing the input pulses. The clock edge recovery output signal contains a respective full clock pulse for each of either the rising or falling edge of the input pulses of the clock signal that occurs while the input gating signal is in an enable state and when the input gating signal transitions from the enable state to the disable state. A counter circuit counts the pulses contained in the clock edge recovery output signal.
1. An apparatus for counting input pulses during a specific time interval, comprising:
an input gating circuit for performing input gating and producing a clock edge recovery output signal in response to a clock signal and an input gating signal, the clock signal containing the input pulses having edges of first and second directions, the second direction of the edges being an opposite to the first direction, the clock edge recovery output signal containing a respective full clock pulse for each of either of the first and second direction edges of the clock signal that occurs while the input gating signal is in an enable state and when the gating signal transitions from the enable state to a disable state; and
a counter circuit for counting the pulses contained in the clock edge recovery output signal.
2. The apparatus of claim 1 wherein the input gating circuit comprises:
a clock gating circuit for gating the clock signal using the input gating signal to produce a gated clock signal, the gated clock signal including a short clock pulse when the input gating signal transitions to a disable state during a clock pulse of the clock signal.
3. The apparatus of claim 2 wherein the input gating circuit further comprises:
a combination logic circuit for producing a first direction edge in the clock edge recovery output signal for each transition in the gated clock signal that corresponds with the first direction edge of the clock signal and for producing a second direction edge in the clock edge recovery output signal for each second direction edge of the clock signal.
4. The apparatus of claim 3 wherein the clock gating circuit comprises:
a latch circuit for latching the logic state of the input gating signal in response to the clock signal, thereby producing a latch output signal; and
a gating logic circuit for producing the gated clock signal in response to the latch output signal, the input gating signal and the clock signal.
5. The apparatus of claim 4 wherein the combination logic circuit comprises:
a latch having a set input for receiving the clock signal and a reset input for receiving the gated clock signal.
6. The apparatus of claim 1 further comprising:
a reset control logic circuit for controlling a reset operation of the counter circuit.
7. The apparatus of claim 6 wherein the reset control logic circuit comprises:
a reset generation circuit for producing a reset control signal in response to the input gating signal, the clock signal, a reset signal and a command change signal.
8. The apparatus of claim 7 wherein the reset control circuit further comprises:
a reset enable circuit for producing a reset enable signal that enables reset for a period following a command on the command signal and for a period following a transition to an enable state on the reset signal.
9. The apparatus of claim 8 wherein the reset generation circuit comprises:
an internal reset generation circuit for generating an internal reset pulse following a positive transition on the input gating signal and a subsequent positive transition of the clock, when enabled by the reset enable signal.
10. The apparatus of claim 9 wherein the internal reset generation circuit comprises:
an input gating signal delay circuit for delaying the input gating signal to provide a delayed input gating signal; and
a logic circuit for logically combining the reset enable signal and the delayed input gating signal to provide the reset control signal.
11. The apparatus of claim 10 wherein the input gating signal delay circuit comprises:
a D-type flip-flop for receiving the input gating signal as D input and clock signal as clock input and for producing a Q output; and
an inverter circuit for producing a delayed inverse of the Q output after a processing delay,
the Q output and the delayed inverse of the Q output together being input to the logic circuit for logically combining the reset enable signal and the delayed input gating signal to provide the reset control signal.
12. The apparatus of claim 11 wherein the inverter circuit comprises:
an odd number of inverters that produces the delayed inverse of the Q output, each of the inverters providing a signal delay.
13. The apparatus of claim 8 wherein the reset enable circuit comprises:
a delay circuit for delaying the reset signal to provide a delayed reset signal; and
a pulse generator for generating a pulse signal in response to the delayed reset signal to provide a reset pulse signal.
14. The apparatus of claim 13 wherein the reset enable circuit further comprises:
a second pulse generator for generating a second pulse signal in response to the reset control signal, the second pulse signal being provided for self-generating the reset control signal.
15. The apparatus of claim 14 wherein the reset enable circuit further comprises:
a logic circuit for logically combining the second pulse signal with the reset pulse signal.
16. The apparatus of claim 1 wherein the counter circuit comprises:
a plurality of flip-flop (FF) circuits that are serially connected for counting the pulses contained in the clock edge recovery output signal, the counter circuit having feedback loops, the plurality of FF circuits including a first FF circuit for receiving the clock edge recovery output signal as clock source, each of the remaining FF circuits of the plurality of FF circuits taking clock source from an output of the previous FF circuit, each of the FF circuits providing an output signal.
17. The apparatus of claim 16 , further comprising:
a logic operation finding circuit for finding a point of the logic operation of the counter circuit in response to the clock edge recovery output signal and the output signals from the FF circuits.
18. The apparatus of claim 17 , wherein the logic operation finding circuit comprises:
a flag generation circuit for issuing a flag in response to the clock edge recovery output signal and the output signals from the FF circuits, the flag being for a next logic system to start operation related to latch and timing control therein.