User's Manual

Table Of Contents

PRELIMINARY

3. Functional Description

This chapter describes the modules and functions integrated in ESP32-WROOM-32E.

3.1 CPU and Internal Memory

ESP32-D0WD-V3 contains two low-power Xtensa

32-bit LX6 microprocessors. The internal memory

includes:

• 448 K

B 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 is

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 the

remaining 768 bits are reserved for customer applications, including flash-encrypt

ion and chip-ID.

3.2 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 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-taneousl

– 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

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-32E integrates a 4 MB SPI flash more memory space.

3.3 Crystal Oscillators

The module uses a 40-MHz crystal oscillator.

ESP32-WROOM-32E User Manual

Espressif Systems