Communication device

1 . A communication device comprising:

a communication line;

a master node connected to the communication line; and

a slave node connected to the communication line, wherein

the master node and the slave node communicate with each other by using a pulse width modulation signal as a line code,

at least one of the master node or the slave node is configured to switch to either a first state in which feedback input of a bus voltage of the communication line is received to control a slew rate of the bus voltage to a desired value, and a second state in which input of a predetermined control signal is received to control the slew rate of the bus voltage to a desired value,

the master node is configured to generate a master-side transmission signal that varies in logic level between a dominant level and a recessive level and transmit the master-side transmission signal to the slave node via the communication line,

the slave node is configured to generate a slave-side transfer signal that varies in logic level between a dominant level and a recessive level and transmit the slave-side transfer signal to the master node via the communication line,

in a case where the master-side transmission signal and the slave-side transfer signal collide in the communication line, whichever of the master-side transmission signal and the slave-side transfer signal that maintains the dominant level for longer is transmitted with priority,

the slave node switches to the second state at a first timing at which the logic level of the slave-side transfer signal switches from the recessive level to the dominant level, and

the master node switches to the second state at a second timing at which the logic level of the master-side transmission signal switches when the slave node sets the slave-side transfer signal to the dominant level.

2 . The communication device according to claim 1 , wherein

the master node switches to the first state at a third timing at which the logic level of the master-side transmission signal switches when the slave node sets the slave-side transfer signal to the recessive level, and

the slave node switches to the first state at a fourth timing at which the logic level of the slave-side transfer signal switches from the dominant level to the recessive level.

3 . The communication device according to claim 2 , wherein

the master node includes:

a master-side transistor connected to the communication line; and

a master-side drive control circuit configured to control a first drive signal of the master-side transistor,

the slave node includes:

a slave-side transistor connected to the communication line; and

a slave-side drive control circuit configured to control a second drive signal of the slave-side transistor, and

the master node and the slave node are configured to change the bus voltage by controlling an ON/OFF state of the master-side transistor and the slave-side transistor.

4 . The communication device according to claim 3 , wherein

the master node includes a detection circuit configured to detect, on the basis of the bus voltage, whether a timing at which the logic level of the master-side transmission signal to arrive is the second timing or the third timing, and

the master-side drive control circuit controls the first drive signal according to a detection result of the detection circuit.

5 . The communication device according to claim 1 , wherein

in the second state, as the desired value, a slew rate of the bus voltage is controlled to a predetermined first slew rate or a second slew rate steeper than the first slew rate,

the slave node includes:

a pulse width detection circuit configured to detect a pulse width between a timing at which a logic level of the master-side transmission signal switches from the recessive level to the dominant level and a timing at which the logic level of the master-side transmission signal next switches, and

at the second timing, the slave node switches a slew rate of the bus voltage to the second slew rate when the pulse width is less than or equal to an interval between the second timing and an immediately preceding third timing.

6 . The communication device according to claim 1 , wherein the communication device conforms to a clock extension peripheral interface protocol.