STM32F103RCY6TR is a 72 MHz ARM Cortex-M3 MCU with 256 KB Flash and 48 KB SRAM in a 64-WLCSP package.
72 MHz Cortex-M3 — what the speed rating buys you
The 72 MHz Cortex-M3 core executes most single-cycle instructions, suitable for real-time control loops and moderate protocol handling.
256 KB Flash and 48 KB SRAM — sizing the firmware budget
The 48 KB SRAM is shared between stack, heap, and DMA buffers — watch the linker map if you plan large frame buffers or double-buffered ADC captures. The Flash is single-bank, so simultaneous read-while-write is not supported; OTA updates require a two-stage bootloader that copies from an external memory or a reserved upper bank.
64-WLCSP — what the package means for assembly and layout
The 64-WLCSP package has fine-pitch balls requiring an HDI PCB stackup with microvias to route all 51 I/Os.
The base product number STM32F103 covers a range of density and package options; a pin-compatible LQFP or BGA variant can serve as a second-source path.