ESP32 WROOM 32D Flash

ESP32-D0WD contains a dual-core Xtensa® 32-bit LX6 MCU. The internal memory includes:
448 KB of ROM for booting and core functions.
520 KB of on-chip SRAM for data and instructions.
8 KB of SRAM in RTC, which is called RTC FAST Memory and can be use for data storage; it is access
by the main CPU during RTC Boot from the Deep-sleep mode.
• 8 KB of SRAM in RTC, which is called RTC SLOW Memory and can be access by the co-processor
during the Deep-sleep mode.
• 1 Kbit of eFuse: 256 bits are use for the system (MAC address and chip configuration) and the remaining
768 bits are reserve for customer applications, including flash-encryption and chip-ID.

ESP32 WROOM 32D Flash

External Flash and SRAM
ESP32 supports multiple external QSPI flash and SRAM chips. More details can be found in Chapter SPI in the
ESP32 Technical Reference Manual. ESP32 also supports hardware encryption/decryption base on AES to
protect developers’ programs and data in flash.
ESP32 can access the external QSPI flash and SRAM through high-speed caches.
• The external flash can be map into CPU instruction memory space and read-only memory space
simultaneously.
– When external flash is map into CPU instruction memory space, up to 11 MB + 248 KB can be
map at a time. Note that if more than 3 MB + 248 KB are map, cache performance will be
reduced due to speculative reads by the CPU.
– When external flash is map into read-only data memory space, up to 4 MB can be map at a
time. 8-bit, 16-bit and 32-bit reads are support.
• External SRAM can be mapped into CPU data memory space. Up to 4 MB can be map at a time.
8-bit, 16-bit and 32-bit reads and writes are support.
Both ESP32-WROOM-32D and ESP32-WROOM-32U integrate a 4 MB of external SPI flash. The integrate SPI
flash is connect to GPIO6, GPIO7, GPIO8, GPIO9, GPIO10 and GPIO11. These six pins cannot be use as
regular GPIOs.

Crystal Oscillators

The module uses a 40-MHz crystal oscillator.

https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32d_esp32-wroom-32u_datasheet_en.pdf