DM50 processor

Introducing

The STM32 family of microcontrollers from STMicroelectronics is based on ARM Cortex-M cores. In 2021, STMicroelectronics launched the new STM32U5 line of ultra-low-power microcontrollers based on the ARM Cortex-M33 core. With suitable clock frequency and computing power, they are ideal for use in next-generation calculators.

The STM32U5 family features Cortex-M33 cores built with a 40nm lithography, 32-bit architecture, and a maximum CPU frequency of 160 MHz. Some calculators that use the STM32 family as their main core include those manufactured by SwissMicros (DM42, DM41X, DM32, etc.).

STM32U575
STM32U575 48-pin LQFP

STM32 comparative

48-64 PINES, without HW crypto:

  • STM32U073CC: 56MHz, 52μA/MHz run, 16nA off, 256KB FLASH, 40KB RAM
  • STM32L072CZ: 32MHz, 93µA/MHz run, 860nA off, 192KB FLASH, 20KB RAM
  • STM32L151CC: 32MHz, 185µA/MHz run, 440nA off, 256KB FLASH, 32KB RAM
  • STM32L451CE: 80MHz, 84µA/MHz run, 22nA off, 512KB FLASH, 160KB RAM
  • STM32L4P5CG: 120MHz, 41μA/MHz run, 22nA off, 1MB FLASH, 320KB RAM
  • STM32L552CE: 110MHz, 62μA/MHz run, 17nA off, 512KB FLASH, 256KB RAM
  • STM32U535CE: 160MHz, 16μA/MHz run, 90nA off, 512KB FLASH, 274KB RAM
  • STM32U575CI: 160MHz, 20μA/MHz run, 160nA off, 2MB FLASH, 786KB RAM
  • STM32U595RJ: 160MHz, 18μA/MHz run, 150nA off, 4MB FLASH, 2MB RAM

For the design of the DM50 calculator, we have chosen the STM32U595RJ model, featuring a 48-pin LQFP package with the following main characteristics:

  • CPU Bits: 32
  • Clock Frequency: 160MHz (110MHz downgrade)
  • FLASH Memory: 4MB
  • RAM Memory: 2MB
  • Power Consumption: 150nA off - 18μA/MHz run

Boot Configuration

  • BOOT0 = 0: 0x0800 0000 (FLASH)
  • BOOT0 = 1: 0x0BF9 0000 (BOOTLOADER)

The bootloader is located in the system memory, programmed by ST during production.

The bootloader is used to reprogram the flash memory by using USART, I2C, SPI, FDCAN or USB OTG_HS in device mode through the DFU (device firmware upgrade).