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3.4
Configuration switches
The V2M-Juno r2 motherboard provides configuration switches, SW0 and SW1.
This section contains the following subsections:
•
3.4.1 Use of configuration switches
•
3.4.2 Remote UART configuration
3.4.1
Use of configuration switches
The SW0 and SW1 switches affect board initialization.
The
config.txt
configuration file contains
USERSWITCH
and
CFGSWITCH
entries for the virtual switch
register bits SYS_SW[7:0] and SYS_CFGSW[7:0] in the IOFPGA. Configuration switch SW0 also
modifies SYS_SW[0]. The configuration system does not use these virtual switches for system
configuration, but they are available for the user application and boot monitor.
See the following for more information:
•
.
•
.
Note
• The default setting for configuration switches SW0 and SW1 is OFF.
• If the switches are in the up position, they are OFF.
Bootscript switch SW0
SW0 in the ON position, or the
config.txt
entry for USERSWITCH[0] being set to 1, sets
SYS_SW[0] to
0b1
.
If SYS_SW[0] is set to
0b1
, the boot loader runs the OS automatically at powerup. If the OS
software supports this feature, under UEFI, this boot process starts automatically irrespective of
the switch setting.
SYS_SW[30] indicates the value of physical configuration switch SW0.
A user application can also modify SYS_SW[0] but the change does not take effect until the
next reset.
Remote UART control switch SW1
SW1 in the ON position enables UART control and the flow-control signals on UART0 to
control the standby-state. This setting is typically used on test farms.
SYS_SW[31] indicates the value of physical configuration switch SW1.
See the following for the location of the configuration switches:
•
1.3 Location of components on the V2M-Juno r2 motherboard
.
•
1.4 Connectors on front and rear panels
.
3.4.2
Remote UART configuration
If SW1 is ON, to enable remote UART control:
• An external controller can toggle UART0
SER0_DSR
, pin 6, HIGH for 100ms to put the V2M-Juno
r2 motherboard into standby-state. This is equivalent to pressing the
Hardware Reset
button. Power
cycling the board also places the system in standby-state.
3 Configuration
3.4 Configuration switches
ARM 100114_0200_03_en
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