Data Sheet

14 | P a g e Espressif Systems Oct 12, 2013
ESP8266 802.11bgn Smart Device
SPI_EN2 usually controls an EEPROM to store individual data, such as MIB information, MAC
address, and calibration data, or for general use. This pin is active low and should be left open if
not used.
Figure 2: SPI timing characteristics
8.4.2 General Purpose IO
There are up to 16 GPIO pins. They can be assigned to various functions by the firmware. Each
GPIO can be configured with internal pull-up/down, input available for sampling by a software
register, input triggering an edge or level CPU interrupt, input triggering a level wakeup interrupt,
open-drain or push-pull output driver, or output source from a software register, or a sigma-delta
PWM DAC.
These pins are multiplexed with other functions such as host interface, UART, SI, Bluetooth
coexistence, etc.
8.4.3 Digital IO Pads
The digital IO pads are bidirectional, non-inverting and tri-state. It includes input and an output
buffer with tristate control inputs. Besides this, for low power operations, the IO can also be set
to hold. For instance, when we power down the chip, all output enable signals can be set to hold
low.