This is a high-level internal block diagram of the RSL15. The RSL15 comes with a full BLE 5.2 baseband controller excluding LE audio. However, the RSL15 does support firmware over the air updates, or FOTA. There is a built-in power management unit, or PMU, accepting an input of 1.2 V to 3.6 V, which is very conducive to a coin cell. The RSL15 is fully equipped with an Arm® Cortex®-M33 processor, including important security features like a secure debug port, TrustZone, CryptoCell-312, and secure boot ROM. The RSL15 comes in two Flash memory sizes: 284 kB Flash memory or 512 kB Flash memory.