Data Sheet

3. Functional Description

3.1. MCU

ESP8266EX integrates the Tensilica L106 32-bit microcontroller (MCU) and ultra-low-power

16-bit RSIC. The CPU clock speed is 80 MHz and can reach a maximum value of 160

MHz. The system can readily run a Real-Time Operating System (RTOS). Currently, the Wi-

Fi stack only takes up 20% of CPU time. The remaining CPU time (80% of total MIPS) can

be used for user applications. The CPU can interface through:

•

Programmable RAM/ROM interfaces (iBus) that connect to memory controller and

can access the external ﬂash.

• Data RAM interface (dBus) that connects to the memory controller.

• AHB interface that accesses the register.

3.2. Memory

3.2.1. Internal SRAM and ROM

ESP8266EX Wi-Fi SoC integrates the memory controller and memory units including ROM

and SRAM. MCU can access the memory units through iBus, dBus, and AHB interfaces.

All memory units can be accessed upon request. A memory arbiter determines the running

sequence in the arrival order of requests.

According to our current version of SDK, the SRAM space available to users is assigned as

follows:

• RAM size < 50 kB, that is, when ESP8266EX is working in Station mode and

connects to the router, available space in the Heap + Data sector is around 50 kB.

• There is no programmable ROM in ESP8266EX, therefore, the user program must be

stored in an external SPI ﬂash.

3.2.2. SPI Flash

ESP8266EX supports SPI ﬂash. Theoretically speaking, ESP8266EX can support an up-

to-16-MB SPI ﬂash.

ESP-WROOM-02 currently integrates a 2-MB SPI ﬂash. ESP-WROOM-02 supports these

SPI modes: Standard SPI, DIO (Dual I/O), DOUT (Dual Output), QIO (Quad I/O) and QOUT

(Quad Output).

Espressif

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2017.10