48 MHz Cortex-M0+ with 16 KB Flash — the entry-level SAM D20E
The Microchip ATSAMD20E14A-MU is a 32-bit ARM Cortex-M0+ MCU from the SAM D20E series, clocked at 48 MHz with 16 KB Flash and 2 KB SRAM.
The 16 KB program memory (16K x 8) and 2 KB SRAM (2K x 8) define the application ceiling. A typical Microchip Harmony or Atmel START HAL plus a lightweight RTOS kernel consumes roughly 6–8 KB of Flash, leaving 8–10 KB for application code. The 2 KB SRAM handles a modest stack and a few data buffers; designs that need larger packet buffers or complex state machines should step up to the ATSAMD20E15A-MU (32 KB Flash) or ATSAMD20E17A-MU (128 KB Flash) within the same package footprint.
The supply range of 1.62 V to 3.6 V allows direct battery operation from two alkaline cells or a single Li-ion cell without an external regulator, though the 48 MHz clock is only guaranteed above 1.8 V.
Package and footprint — 32-VQFN with exposed pad
The 26 I/O are distributed on two sides of the package; the 0.50 mm pitch demands a 4-layer board for clean fan-out of all signals, though a 2-layer board can route the inner rows if the outer rows are depopulated.
Microchip lists the ATSAMD20E14A-MU as Active. The part is ROHS3 compliant.