A device involved in a safety-relevant or safety-critical process for monitoring and/or controlling said safety-relevant or safety-critical process, comprising an I/O module for gathering input peripheral signals applied on at least one peripheral signal port and/or for outputting output peripheral signals on at least one peripheral signal port by at least one accommodated peripheral unit (110-1, 110-2, 110-n); wherein the I/O module accommodates a microcontroller system having a first plurality of peripheral units (110-1, 110-2, 110-n) each having at least one peripheral signal port at which applied input peripheral signals are gathered and/or output peripheral signals are output, a second plurality of microprocessor units (300-1, 300-2), and at least one diagnostic unit; wherein each of the first plurality of peripheral units (110-1, 110-2, 110-n) and each of the second plurality of microprocessor units, and the diagnostic unit have a respective biunique communication identifier; and each of the first plurality of peripheral units (110-1, 110-2, 110-n), each of the second plurality of microprocessor units (300-1, 300-2), and the diagnostic unit have a microcontroller interface for communicating via a microprocessor bus (200-1, 200-2) and for performing driving and/or controlling functions; wherein each of the first plurality of peripheral units (110-1, 110-2, 110-n) is connected to at least one microprocessor unit (300-1, 300-2) via at least one microprocessor bus (200-1, 200-2), which microprocessor bus (200-1, 200-2) also has the respective diagnostic unit connected thereto; wherein the diagnostic unit monitors the data transfer on the microprocessor busses (200-1, 200-2) and gains access to the peripheral units (110-1, 110-2, 110-n), via which the peripheral units (110-1, 110-2, 110-n) are put into a defined safe state by the diagnostic unit in the event of an error; and each of these units connected to a microprocessor bus (200-1, 200-2) is adapted, when transmitting data via the microprocessor bus (200-1, 200-2), which data may represent peripheral signals applied to the at least one peripheral signal port and/or output peripheral signals to be output to the at least one peripheral signal port, to include in the transmission its own respective biunique communication identifier as a safety-relevant data item, and when receiving data that have been transmitted via the microprocessor bus (200-1, 200-2) to identify the communication identifier of a respective transmitting unit as a safety-relevant data item and to evaluate it in a safety-related manner. wherein the I/O module accommodates a microcontroller system having a first plurality of peripheral units (110-1, 110-2, 110-n) each having at least one peripheral signal port at which applied input peripheral signals are gathered and/or output peripheral signals are output, a second plurality of microprocessor units (300-1, 300-2), and at least one diagnostic unit; wherein each of the first plurality of peripheral units (110-1, 110-2, 110-n) and each of the second plurality of microprocessor units, and the diagnostic unit have a respective biunique communication identifier; and each of the first plurality of peripheral units (110-1, 110-2, 110-n), each of the second plurality of microprocessor units (300-1, 300-2), and the diagnostic unit have a microcontroller interface for communicating via a microprocessor bus (200-1, 200-2) and for performing driving and/or controlling functions; wherein each of the first plurality of peripheral units (110-1, 110-2, 110-n) is connected to at least one microprocessor unit (300-1, 300-2) via at least one microprocessor bus (200-1, 200-2), which microprocessor bus (200-1, 200-2) also has the respective diagnostic unit connected thereto; wherein the diagnostic unit monitors the data transfer on the microprocessor busses (200-1, 200-2) and gains access to the peripheral units (110-1, 110-2, 110-n), via which the peripheral units (110-1, 110-2, 110-n) are put into a defined safe state by the diagnostic unit in the event of an error; and each of these units connected to a microprocessor bus (200-1, 200-2) is adapted, when transmitting data via the microprocessor bus (200-1, 200-2), which data may represent peripheral signals applied to the at least one peripheral signal port and/or output peripheral signals to be output to the at least one peripheral signal port, to include in the transmission its own respective biunique communication identifier as a safety-relevant data item, and when receiving data that have been transmitted via the microprocessor bus (200-1, 200-2) to identify the communication identifier of a respective transmitting unit as a safety-relevant data item and to evaluate it in a safety-related manner.