
Device configuration and ordering information ST72321xx-Auto
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Table 141. Option byte 0 bit description
Bit Name Function
OPT7 WDG HALT
Watchdog and Halt mode
This option bit determines if a RESET is generated when entering
Halt mode while the Watchdog is active.
0: No Reset generation when entering Halt mode
1: Reset generation when entering Halt mode
OPT6 WDG SW
Hardware or software watchdog
This option bit selects the watchdog type.
0: Hardware (watchdog always enabled)
1: Software (watchdog to be enabled by software)
OPT5 - Reserved, must be kept at default value.
OPT4:3 VD[1:0]
Voltage detection
These option bits enable the voltage detection block (LVD and AVD)
with a selected threshold for the LVD and AVD (EVD + AVD).
00: Selected LVD = Highest threshold (V
DD
~4V)
01: Selected LVD = Medium threshold (V
DD
~3.5V)
10: Selected LVD = Lowest threshold (V
DD
~3V)
11: LVD and AVD off
Caution: If the medium or low thresholds are selected, the detection
may occur outside the specified operating voltage range. Below 3.8V,
device operation is not guaranteed. For details on the AVD and LVD
threshold levels refer to Table 19.3.2: Operating conditions with low
voltage detector (LVD).
OPT2 - Reserved, must be kept at default value.
OPT1 PKG0
Package selection bit 0
This option bit is used with the PKG1 bit to select the package (see
Table 143: Package selection (OPT7)).
OPT0 FMP_R
Flash memory readout protection
Readout protection, when selected, provides a protection against
program memory content extraction and against write access to Flash
memory.
Erasing the option bytes when the FMP_R option is selected causes
the whole user memory to be erased first, after which the device can
be reprogrammed. Refer to Section 4.3.1: Readout protection on
page 30 and the ST7 Flash Programming Reference Manual for more
details.
Note: Readout protection is not supported if LVD is enabled.
0: Readout protection enabled
1: Readout protection disabled
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