The invention relates to an arrangement for checking a program memory (9) in a computation unit having a checking module (11), wherein the computation unit comprises a command counter (8) which is connected to the checking module (11) and which has a register (1), and the register (1) is connected to a first changeover switch (3) which sets the register content. In an arrangement which allows the command addresses of the complete program memory to be checked, the command counter (8) contains a supplementary counter (2, 6, 7) which is connected to the register (1) and which passes through the command address space of the program memory (9) independently of the program code during normal operation.