Espressif Systems ESP32-WROOM-32UE - 3. Functional Description; 3.1 CPU and Internal Memory; 3.2 External Flash and SRAM; 3.3 Crystal Oscillators

PRE
LIMINARY
3.
Functional Description
3. Funct
ional Description
Th
is chapter describes the modules and functions integrated in ESP32-WROOM-32UE.
3.
1 CPU and Internal Memory
ESP3
2-D0WD-V3 contains two low-power Xtensa
®
32-bi
t LX6 microprocessors. 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 used for data storage; it i
s
accessed 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 accessed by the co-processor
during the Deep-sleep mode.
• 1 Kbit of eFuse: 256 bits are used for the system (MAC address and chip configuration) and t
he
remaining 768 bits are reserved for customer applications, including flash-encryption and chip-ID.
3.
2 External Flash and SRAM
ESP3
2 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 based on
AES to pro-tect developers’ programs and data in flash.
ESP32 can access the external QSPI flash and SRAM through high-speed caches.
• The external flash can be mapped into CPU instruction memory space and read-only memory space
simul-taneously.
– When external flash is mapped into CPU instruction memory space, up to 11 MB + 248 KB can be
mapped at a time. Note that if more than 3 MB + 248 KB are mapped, cache performance will be
reduced due to speculative reads by the CPU.
– When external flash is mapped into read-only data memory space, up to 4 MB can be mapped at
a
time. 8-bit, 16-bit and 32-bit reads are supported.
• External SRAM can be mapped into CPU data memory space. Up to 4 MB can be mapped at a time. 8-
bit, 16-bit and 32-bit reads and writes are supported.
ESP32-WROOM-32UE integrates a 4 MB SPI flash more memory space.
3.3 Crystal Oscillators
The module uses a 40-MHz crystal oscillator.
Espressif Systems 7
ESP32-WROOM-32UE User Manual
V0.1