Espressif ESP32 Technical Reference Manual page 525

20 eFuse Controller
Name
vol_level_hp_inv
dig_vol_l6
uart_download_dis
20.3.1.1 System Parameter efuse_wr_disable
The system parameter efuse_wr_disable determines whether all of the system parameters are write-protected.
Since efuse_wr_disable is a system parameter as well, it also determines whether itself is write-protected.
If a system parameter is not write-protected, its unprogrammed bits can be programmed from 0 to 1. The bits
previously programmed to 1 will remain 1. When a system parameter is write-protected, none of its bits can be
programmed: The unprogrammed bits will always remain 0 and the programmed bits will always remain 1.
The write-protection status of each system parameter corresponds to a bit in efuse_wr_disable. When the
corresponding bit is set to 0, the system parameter is not write-protected. When the corresponding bit is set to
1, the system parameter is write-protected. If a system parameter is already write-protected, it will remain write-
protected. The column entitled "Program-Protection by efuse_wr_disable" in Table
bits that determine the write-protection status of each system parameter.
20.3.1.2 System Parameter efuse_rd_disable
Of the 33 system parameters, 27 are not constrained by software-read-protection. These are marked by "-" in
the column entitled "Software-Read-Protection by efuse_rd_disable" in Table 20-1. Those system parameters,
some of which are used by software and hardware modules at the same time, can be read by software via the
eFuse Controller at any time.
When not software-read-protected, the other six system parameters can both be read by software and used
by hardware modules. When they are software-read-protected, they can only be used by the hardware mod-
ules.
The column "Software-Read-Protection by efuse_rd_disable" in Table
_disable that determine the software read-protection status of the six system parameters. If a bit in the system
parameter efuse_rd_disable is 0, the system parameter controlled by the bit is not software-read-protected. If
a bit in the system parameter efuse_rd_disable is 1, the system parameter controlled by the bit is software-read-
protected. If a system parameter is software-read-protected, it will remain in this state.
Espressif Systems
Program
Bit width -Protection by
efuse_wr_disable efuse_rd_disable
2 3
4 11
1 2
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Software-Read
-Protection by
-
-
-
20-1 lists the corresponding bits in efuse_rd
525
Description
stores the voltage level for
CPU to run at 240 MHz, or
for flash/PSRAM to run at 80
MHz
stores the difference be-
tween the digital regulator
voltage at level 6 and 1.2 V.
permanently disables Down-
load Boot mode when set to
1. Valid only for ESP32 ECO
V3.
20-1 lists the corresponding
ESP32 TRM (Version 5.2)