Main Board Reset Sources; Main Board Boot Options; Table 4. Boot Settings - ST STM32 User Manual

Hardware layout and configuration
The following power sequence procedure must be respected:
1. Put a jumper in JP3 at location U5V to use power from user USB CN8 or at location
E5V to use power from VIN of ARDUINO
2. Connect the corresponding external power source.
3. Check that the green LED LD8 is turned ON.
4. Connect the PC to ST-LINK/V2-1 USB connector CN5.
If this order is not respected, the board might be powered by V
the following risks might be encountered:
1. If the board requires more than 500 mA current, the PC might be damaged, or limit the
current. As a consequence, the board is not powered correctly.
2. The enumeration step requires 500 mA. Thus, there is a risk that the request is
rejected and enumeration does not succeed if the PC does not provide such current.
5.5

Main board reset sources

The reset signal of the STM32L496AGI6-based Discovery main board is active LOW and
the reset sources include:
•
Reset button B1
•
Embedded ST-LINK/V2-1, SW1 set to ON (default setting)
•
ARDUINO
5.6

Main board boot options

After reset, the microcontroller STM32L496AGI6 might boot from the 3 following embedded
memory locations depending on bits BOOT0 and BOOT1:
•
Boot from the user flash memory
•
Boot from the ICP (in-circuit programming)
•
Boot from the SRAM
The selection of the memory space for the boot is done by two bits, BOOT0 and BOOT1.
A user option bit (bit[23], nBOOT1) defines the value of BOOT1. Specifically, when this bit is
set (put to 1), the empty flag status toggles and keeps this new status until the next OBL or
until a new set.
nBOOT1 nBOOT0
(OPTR[23]) (OPTR[27])
X
X
1
14/22
®
connector CN15 pin 3

Table 4. Boot settings

BOOT0 pin
(PH3)
X 0
X 0
X 1
®
connector CN15.
BOOT0 SW
Main flash
configuration
empty
OPTR[26])
1 0
1 1
1 X
UM2365 Rev 3
UM2365
first from ST-LINK, and
BUS
Boot memory space alias
User flash memory is aliased at
address 0x0000_0000
Test flash memory is aliased at
address 0x0000_0000
Test flash memory is aliased at
address 0x0000_0000