Controlling synchronous I/O interface

1. An electronic device comprising:

a first input node configured to receive a clock signal;

a second input node configured to receive an activation signal or a deactivation signal;

a filter circuit responsive to: (a) the activation signal to activate the filter circuit to block the clock signal, or (b) the deactivation signal to deactivate the filter circuit to pass the clock signal; and

an output node configured for coupling to a synchronous input/output (I/O) interface of an integrated circuit to control operation of the synchronous I/O interface,

wherein the first input node is configured for coupling to an external clocked circuit to receive the clock signal, and the second input node is configured for coupling to the integrated circuit to receive the activation signal or the deactivation signal, and

wherein the external clocked circuit is a debugger, the synchronous I/O interface is a serial wire debug (SWD) interface, and the second input node of the electronic device is configured for coupling to a spare I/O pin of the integrated circuit to receive the activation signal or the deactivation signal.

2. The electronic device of claim 1 , wherein the output node is configured to:

output the clock signal to the synchronous I/O interface, when the filter circuit is deactivated, to enable the synchronous I/O interface, and

block the clock signal when the filter circuit is activated, to disable the synchronous I/O interface.

3. The electronic device of claim 1 , wherein the filter circuit comprises at least one of: a capacitor circuit, a resistor-capacitor (RC) circuit, an inductor-capacitor (LC) circuit, a resistor-inductor (RL) circuit, a resistor-inductor-capacitor (RLC) circuit, or a combination thereof.

4. The electronic device of claim 3 , wherein the filter circuit comprises at least one capacitor, and the activation signal is configured to activate the at least one capacitor so that the filter circuit blocks the clock signal.

5. The electronic component of claim 1 , wherein the filter circuit comprises at least one transistor, and the activation signal or the deactivation signal is configured to activate or deactivate a gate of the at least one transistor so that the filter circuit respectively blocks or passes the clock signal.

6. The electronic component of claim 1 , wherein the filter circuit comprises:

at least one transistor, and

at least one of: a capacitor circuit, a resistor-capacitor (RC) circuit, an inductor-capacitor (LC) circuit, a resistor-inductor (RL) circuit, a resistor-inductor-capacitor (RLC) circuit, or a combination thereof.

7. An apparatus, comprising:

an integrated circuit including:

a synchronous input/output (I/O) interface; and

a general purpose I/O pin configured to provide an activation signal or a deactivation signal; and

a filter circuit:

coupled to receive a clock signal from an external clocked circuit and coupled to receive the activation signal or the deactivation signal from the integrated circuit; and

configured to block the clock signal based on the activation signal or pass the clock signal to the integrated circuit based on the deactivation signal,

wherein the external clocked circuit is a debugger, the synchronous I/O interface is a serial wire debug (SWD) interface, and the clock signal passed by the filter circuit is received through a clock pin of the SWD interface.

8. The apparatus of claim 7 , wherein:

operation of the synchronous I/O interface is enabled when the filter circuit is deactivated by the deactivation signal and passes the clock signal, or

operation of the synchronous I/O interface is disabled when the filter circuit is activated by the activation signal and blocks the clock signal.

9. The apparatus of claim 7 , wherein the filter circuit comprises at least one of: a capacitor circuit, a resistor-capacitor (RC) circuit, an inductor-capacitor (LC) circuit, a resistor-inductor (RL) circuit, a resistor-inductor-capacitor (RLC) circuit, or a combination thereof.

10. The apparatus of claim 9 , wherein the filter circuit comprises at least one capacitor, and the activation signal or the deactivation signal is configured to activate or deactivate the at least one capacitor so that the filter circuit respectively blocks or passes the clock signal.

11. The apparatus of claim 7 , wherein:

wherein the filter circuit comprises at least one transistor, and the activation signal or the deactivation signal is configured to activate or deactivate a gate of the at least one transistor so that the filter circuit respectively blocks or passes the clock signal.

12. The apparatus of claim 7 , wherein the filter circuit comprises:

at least one transistor, and

at least one of: a capacitor circuit, a resistor-capacitor (RC) circuit, an inductor-capacitor (LC) circuit, a resistor-inductor (RL) circuit, a resistor-inductor-capacitor (RLC) circuit, or a combination thereof.

13. The apparatus of claim 7 , wherein the activation signal or the deactivation signal is transmitted through a spare I/O pin of the integrated circuit.

14. The apparatus of claim 13 , wherein the integrated circuit is further configured to:

determine whether to transmit the activation signal or the deactivation signal based on a trigger event, and

control the spare I/O pin to output the activation signal or the deactivation signal to the filter circuit based on the determination.

15. A method for controlling a synchronous input/output (I/O) interface included in an integrated circuit, comprising:

receiving, by a filter circuit, from an external clocked circuit, a clock signal;

transmitting, from the integrated circuit, to the filter circuit, an activation signal configured to activate the filter circuit; and

blocking, by the filter circuit, the clock signal to disable operation of the synchronous I/O interface in response to the activation signal,

wherein the filter circuit comprises: a first input node configured for coupling to the external clocked circuit to receive the clock signal, and a second input node configured for coupling to the integrated circuit to receive the activation signal or the deactivation signal, and

wherein the external clocked circuit is a debugger, the synchronous I/O interface is a serial wire debug (SWD) interface, and the second input node of the filter circuit is configured for coupling to a spare I/O pin of the integrated circuit to receive the activation signal or the deactivation signal.

16. The method of claim 15 , the method further comprising:

transmitting, from the integrated circuit, to the filter circuit, a deactivation signal configured to deactivate the filter circuit; and

passing, by the filter circuit, to the synchronous I/O interface, the clock signal to enable operation of the synchronous I/O interface in response to the deactivation signal.

17. The method of claim 16 , further comprising:

identifying a trigger event that determines selection of the activation signal or the deactivation signal; and

controlling, responsive to the identified trigger event, a spare I/O pin of the integrated circuit to transmit the activation signal or the deactivation signal to the filter circuit.