Embedded Flash memory (FLASH) for category 2 devices RM0440
222/2126 RM0440 Rev 4
Bit 31 Reserved, must be kept at reset value.
Bit 30 IRHEN: Internal reset holder enable bit
0: Internal resets are propagated as simple pulse on NRST pin
1: Internal resets drives NRST pin low until it is seen as low level
Bits 29:28 NRST_MODE[1:0]
00: Reserved
01: Reset Input only: a low level on the NRST pin generates system reset,
internal RESET not propagated to the NSRT pin
10: GPIO: standard GPIO pad functionality, only internal RESET possible
11: Bidirectional reset: NRST pin configured in reset input/output mode (legacy
mode)
Bit 27 nBOOT0: nBOOT0 option bit
0: nBOOT0 = 0
1: nBOOT0 = 1
Bit 26 nSWBOOT0: Software BOOT0
0: BOOT0 taken from the option bit nBOOT0
1: BOOT0 taken from PB8/BOOT0 pin
Bit 25 CCMSRAM_RST: CCM SRAM Erase when system reset
0: CCM SRAM erased when a system reset occurs
1: CCM SRAM is not erased when a system reset occurs
Bit 24 SRAM_PE: SRAM1 and CCM SRAM parity check enable
0: SRAM1 and CCM SRAM parity check enable
1: SRAM1 and CCM SRAM parity check disable
Bit 23 nBOOT1: Boot configuration
Together with the BOOT0 pin, this bit selects boot mode from the Flash main
memory, SRAM1 or the System memory. Refer to Section 2.6: Boot
configuration.
Bits: 22:20 Reserved, must be kept cleared
Bit 19 WWDG_SW: Window watchdog selection
0: Hardware window watchdog
1: Software window watchdog
Bit 18 IWDG_STDBY: Independent watchdog counter freeze in Standby mode
0: Independent watchdog counter is frozen in Standby mode
1: Independent watchdog counter is running in Standby mode
Bit 17 IWDG_STOP: Independent watchdog counter freeze in Stop mode
0: Independent watchdog counter is frozen in Stop mode
1: Independent watchdog counter is running in Stop mode
Bit 16 IDWG_SW: Independent watchdog selection
0: Hardware independent watchdog
1: Software independent watchdog
Bit 15 Reserved, must be kept cleared
Bit 14 nRST_SHDW
0: Reset generated when entering the Shutdown mode
1: No reset generated when entering the Shutdown mode