Memory Map

This page describes the physical memory layout of the ESP8266 family.

Reset Vector

The reset vector is 40000000h, which maps to internal ROM.

Address	Name	Size	Type	R/W	Description
00000000h			Exc		Causes fault when reading.
20000000h			No		Unmapped, repeated pattern of 00 80 00 00.
3FF00000h	dport0	1000h	I/O	RW?	Memory-mapped I/O, repeated every 100h.
3FF10000h			No		Unmapped, zeroes.
3FF20000h	?		?	RW?	Unidentified data.
3FF30000h			No		Unmapped, zeroes.
3FFC0000h	?	20000h	?	RW?	uint32 mapping to the address it is located at. What is this?
3FFE0000h			No		Unmapped, zeroes.
3FFE8000h	dram0	14000h	RAM	RW	User data RAM. Available to applications.
3FFFC000h		4000h	RAM		ETS system data RAM.
40000000h	brom?	10000h	ROM	RW?	Internal ROM. May be writable somehow, but details unknown.
40010000h			No		Unmapped, zeroes.
40100000h	iram1	10000h	RAM	RW	Instruction RAM. Used by bootloader to load SPI Flash <40000h.
40110000h			No		Unmapped, zeroes.
40140000h			No		Unmapped, repeated pattern of 59 31 d8 ec.
40200000h			No		Unmapped, zeroes. SPI Flash here. Why is this zero? Privileged?
40300000h			No		Unmapped, repeated pattern of 00 80 00 00.
60000000h	?	1000h	I/O	RW?	I/O
60001000h	?	800h	?	RW?	I/O
60001800h	?	800h	?	RW?	Mapped to 60001000h?
60002000h			Exc		Causes fault when reading.
70000000h		90000000h	No		Unmapped, repeated pattern of 00 80 00 00.

This is for ESP IoT SDK version 0.8 and above.

Address	Size	Name	Description
00000h	248k	app.v6.flash.bin	User application
3E000h	8k	master_device_key.bin	OTA device key
40000h	240k	app.v6.irom0text.bin	SDK libraries
7C000h	8k	esp_init_data_default.bin	Default configuration
7E000h	8k	blank.bin	Filled with FFh. May be WiFi configuration.

This is for ESP IoT SDK version 0.8 and above, supporting OTA upgrades.

Address	Size	Name	Description
00000h	4k	boot.bin	Bootloader
01000h	64k	app.v6.flash1.bin	User application, slot 1
11000h	180k	app.v6.irom0text1.bin	SDK libraries, slot 1
3E000h	8k	master_device_key.bin	OTA device key
40000h	4k		Unused
41000h	64k	app.v6.flash1.bin	User application, slot 2
51000h	180k	app.v6.irom0text1.bin	SDK libraries, slot 2
7E000h	8k	blank.bin	Filled with FFh. May be WiFi configuration.

Unconfirmed. From the XT2000 memory map.