A data processing system comprises multiple data processing nodes that communicate with one another using the FlexRay protocol. Each respective node works according to a respective schedule based on a repetitive sequence of cycles, each cycle having a sequence of time slots. Each node executes instructions, one per time slot, if any. The instructions are stored in a memory. Each instruction is identified by the relevant cycle number and time slot number in the relevant cycle. Accordingly, the combination of cycle number and slot number identify a memory address. Typical instructions appear more than once in the repetitive sequence of cycles for a node. This temporal pattern of occurrences of the same instruction at a node is used to modify the generation of the memory addresses, so that the same memory address is generated each time the instruction is needed. This makes efficient use of storage space.