Specifications

Programmers Model
ARM DUI 0447J Copyright © 2009-2014, ARM. All rights reserved. 4-11
ID052914 Non-Confidential
Configurations See Table 4-5.
Attributes See Table 4-3 on page 4-8.
Figure 4-4 shows the bit assignments.
Figure 4-4 SYS_SW Register bit assignments
Table 4-5 shows the bit assignments.
4.4.3 LED Register
The SYS_LED Register characteristics are:
Purpose Controls the user LEDs on the motherboard. At reset, all LEDs are turned
off. The Boot Monitor updates the LED value.
Usage constraints There are no usage constraints.
Configurations Available in all configurations.
Attributes See Table 4-3 on page 4-8.
31 30 29 0
Undefined Soft user switch
87
SW[1]
SW[0]
28 27
nUART0CTS
nUART0DSR
Table 4-5 SYS_SW Register bit assignments
Bits Access Name Reset Description
31 Read-only SW[1] Indicates the value of physical
configuration switch SW[1].
See the ARM
®
Versatile
™
Express
Configuration Technical Reference
Manual.
30 Read-only SW[0] Indicates the value of physical
configuration switch SW[0].
See the ARM
®
Versatile
™
Express
Configuration Technical Reference
Manual.
29 Read-only nUART0CTS -
UART0 control signal. See the ARM
®
Versatile
™
Express Configuration
Technical Reference Manual.
28 Read-only nUART0DSR -
UART0 control signal. See the ARM
®
Versatile
™
Express Configuration
Technical Reference Manual
[27:8] Read-only Undefined - -
[7:0] Read-write Soft user switch Set to value of
USERSWITCH in the
config.txt file.
User applications can read these switch
settings.
If SYS_SW[0] is set, the Boot Monitor
runs its boot script.
See the ARM
®
Versatile
™
Express Boot
Monitor Reference Manual for more
switch settings.