Espressif Systems ESP32-C3FH4 Hardware Design Manuallines page 13

2 Schematic Checklist
• power-on-reset
• RTC watchdog reset
• brownout reset
• analog super watchdog reset
• crystal clock glitch detection reset
By default, GPIO9 is connected to the internal pull-up resistor. If GPIO9 is not connected or connected to an
external high-impedance circuit, the latched bit value will be "1"
To change the strapping bit values, you can apply the external pull-down/pull-up resistances, or use the host
MCU's GPIOs to control the voltage level of these pins when powering on ESP32-C3 family.
After reset, the strapping pins work as normal-function pins.
Refer to Table 2 for a detailed boot-mode configuration of the strapping pins.
Pin Default
GPIO2 N/A
GPIO8 N/A
GPIO9 Internal pull-up
Pin Default
GPIO8 N/A
1
The strapping combination of GPIO8 = 0 and GPIO9 = 0 is invalid and will trigger unexpected behavior.
Figure 10 shows the setup and hold times for the strapping pin before and after the CHIP_EN signal goes high.
Details about the parameters are listed in Table 3.
Espressif Systems
Table 2: Strapping Pins
Booting Mode
SPI Boot
1
Don't care
1
Enabling/Disabling ROM Code Print During Booting
Functionality
When the value of eFuse field EFUSE_UART_PRINT_CONTROL is
0 (default), print is enabled and not controlled by GPIO8.
1, if GPIO8 is 0, print is enabled; if GPIO8 is 1, it is disabled.
2, if GPIO8 is 0, print is disabled; if GPIO8 is 1, it is enabled.
3, print is disabled and not controlled by GPIO8.
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ESP32-C3 Family Hardware Design Guidelines V1.0