In a portable data carrier (1) having a contact-type interface device (2, 3) and a contactless interface device (4, 5) a sequencing device (6) coordinates competingly occurring contact-type and contactless data communications (16, 19) in such a way that the two data communications (16, 19) can be carried out sequentially step-by-step and without data loss. The processing of the first data communication via the first interface (4) is interrupted in order to start a second data communication via the second interface (2). After the step of starting, the interrupted processing of the first data communication is continued while at the same time the started second data communication is maintained.