The APS3 core uses a 128 KB instruction/boot ROM along with a 160 KB instruction RAM and a 64 KB data RAM. The ATWINC15x0B devices are populated with either 4 Mb or 8 Mb of Flash memory depending on the model that is ordered. This memory can be used for system software. For more information, see the Ordering Details table. In addition, the device uses a 128 KB shared RAM, accessible by the processor and MAC, which allows the APS3 core to perform various data management tasks on the TX and RX data packets.