Interface module (15; 150) for a communication control device (11; 110) of a subscriber station of a serial bus system , having at least one configuration register (151 to 154) for configuring the bit time (T_B1) of a first communication phase of a frame and/or the bit time (T_B2) of a second communication phase of the frame , with which messages (45; 46) are exchanged between subscriber stations of the bus system , and a modulator for modulating a digital transmit signal (TxD_PRT) into a modulated digital transmit signal (TxD_PWM) having the bit time (T_B2) of the second communication phase , which is configured in the at least one configuration register (151 to 154) and differs from the bit time (T_B1) of the first communication phase , wherein the interface module (15; 150) is configured, in the first communication phase , to output the digital transmit signal (TxD_PRT) input to the modulator to a transmitting/receiving device (12; 120) of the subscriber station in order to convert the digital transmit signal (TxD_PRT) into signals (CAN_H, CAN_L) for bus wires of a bus of the bus system using the transmitting/receiving device (12; 120) and to transmit the signals (CAN_H, CAN_L) onto the bus , and wherein the interface module (15; 150) is configured, in the second communication phase , to output the modulated digital transmit signal (TxD_PWM) generated by the modulator to the transmitting/receiving device (12; 120) of the subscriber station in order to convert the modulated digital transmit signal (TxD_PWM) into signals (CAN_H, CAN_L) for the bus wires of the bus of the bus system using the transmitting/receiving device (12; 120) and to transmit the signals (CAN_H, CAN_L) onto the bus , wherein the modulator is designed for pulse-width modulation of the transmit signal (TxD_PRT), and wherein the modulator is configured to use, as a parameter for the pulse-width modulation, a modulation offset (PWM_OS) included in the at least one configuration register . at least one configuration register (151 to 154) for configuring the bit time (T_B1) of a first communication phase of a frame and/or the bit time (T_B2) of a second communication phase of the frame , with which messages (45; 46) are exchanged between subscriber stations of the bus system , and a modulator for modulating a digital transmit signal (TxD_PRT) into a modulated digital transmit signal (TxD_PWM) having the bit time (T_B2) of the second communication phase , which is configured in the at least one configuration register (151 to 154) and differs from the bit time (T_B1) of the first communication phase , wherein the interface module (15; 150) is configured, in the first communication phase , to output the digital transmit signal (TxD_PRT) input to the modulator to a transmitting/receiving device (12; 120) of the subscriber station in order to convert the digital transmit signal (TxD_PRT) into signals (CAN_H, CAN_L) for bus wires of a bus of the bus system using the transmitting/receiving device (12; 120) and to transmit the signals (CAN_H, CAN_L) onto the bus , and wherein the interface module (15; 150) is configured, in the second communication phase , to output the modulated digital transmit signal (TxD_PWM) generated by the modulator to the transmitting/receiving device (12; 120) of the subscriber station in order to convert the modulated digital transmit signal (TxD_PWM) into signals (CAN_H, CAN_L) for the bus wires of the bus of the bus system using the transmitting/receiving device (12; 120) and to transmit the signals (CAN_H, CAN_L) onto the bus , wherein the modulator is designed for pulse-width modulation of the transmit signal (TxD_PRT), and wherein the modulator is configured to use, as a parameter for the pulse-width modulation, a modulation offset (PWM_OS) included in the at least one configuration register . <EOS>