A memory controller can perform prefetching, in a way which increases the efficiency with which data can be read from an external memory. More specifically, the memory controller operates such that it performs prefetching only under certain conditions, which are chosen such that there is a high probability that the data requested in the prefetching operation will be the data which is next required. The memory controller may be implemented in a programmable logic device (PLD), and be optimized for retrieving data from an external flash or SRAM memory device, which is used for storing configuration data for the PLD. By examining a read request, it is possible to determine whether a prefetching operation can be performed, with a high probability that it will be the required data which is prefetched.