Stylus and sensor controller

1. A stylus that operates in synchronization with a sensor controller connected to a sensor electrode group, the stylus comprising:

an electrode;

a memory; and

a processor, wherein the processor, in operation:

detects a first signal supplied to the sensor electrode group in each frame of a plurality of frames, wherein each frame corresponds to a display operation period of a display panel,

determines whether the first signal represents a setting instruction of a local identifier,

in response to determining that the first signal represents the setting instruction of the local identifier, determines whether a counter value is equal to a first value,

in response to determining that the counter value is not equal to the first value, ignores the setting instruction and changes the counter value,

in response to determining that the counter value is equal to the first value, stores a value of the local identifier specified by the setting instruction to the memory,

repeatedly detects a second signal supplied to the sensor electrode group in each of one or more slots included in the frame, wherein the second signal that notifies one or more timing of one or more blank periods corresponding to the one or more slots in the frame, and

compares a value of a local identifier included in the second signal detected and the value of the local identifier specified by the setting instruction and stored in the memory every time the processor detects the second signal, and transmits a first downlink signal to the sensor controller using the electrode in response to determining that the value of the local identifier included in the second signal and the value of the local identifier specified by the setting instruction and stored in the memory correspond with each other.

2. The stylus according to claim 1 , wherein

the second signal has a shorter time length than the first signal.

3. The stylus according to claim 2 , wherein

only a value that represent the local identifier is included in the second signal.

4. The stylus according to claim 1 , wherein

the processor does not employ the first signal as a trigger of transmission of the first downlink signal, and

the processor is triggered to transmit the first downlink signal by detection of the second signal.

5. The stylus according to claim 1 , wherein

the processor transmits a second downlink signal as a response to the setting instruction in response to detection of the first signal.

6. The stylus according to claim 5 , wherein

the processor transmits the second downlink signal in a same slot as the first signal that represents the setting instruction or in an immediately-subsequent slot.

7. The stylus according to claim 5 , wherein

the processor transmits the second downlink signal in a slot in which the processor has detected the second signal including a predetermined local identifier.

8. The stylus according to claim 1 , wherein

the processor determines whether the second signal includes a reset order, and deletes the value of the local identifier stored in the memory if the second signal is determined to include the reset order.

9. The stylus according to claim 8 , wherein

the processor holds, in the memory, a state that identifies whether pairing of the stylus with the sensor controller has been carried out, and

the processor sets the state to a state indicating that the pairing has been carried out after writing the local identifier to the memory, and

the processor sets the state to a state indicating that the pairing has not been carried out if the second signal is determined to include the reset order.

10. The stylus according to claim 1 , wherein

the processor does not transmit the first downlink signal in one frame if none of the second signals transmitted a plurality of times in the one frame includes the value of the local identifier written to the memory.