Usage Notes and Known Design Exceptions to Functional Specifications
Advisory 1.0.25
Boot: System Boot Temporarily Stalls if an Attempt to Boot from Ethernet is Not
Successful
Revisions Affected
2.1, 2.0, 1.0
Details
The system is delayed for up to 4.5 minutes before continuing to the next boot device if
an attempt to boot from Ethernet fails for any reason.
This delay is likely to cause an undesirable user experience when the boot sequence
attempts Ethernet boot before booting from the primary boot device. For example, it may
be desirable to select SYSBOOT [4:0] = 00111b for a product that would normally skip
over Ethernet boot which is the first boot device in this sequence and boots from MMC0
which is the second boot device in this sequence. This example boot sequence provides
an option to boot from Ethernet as a way to break into the boot sequence to update
MMC0 boot code by simply connecting it to an Ethernet host capable of booting the
product for the purpose of updating MMC0 boot code. However, this boot sequence
attempts to boot from Ethernet first which would insert an undesirable long delay when
booting from MMC0.
Workarounds
There is no device-level workaround, but it may be possible to develop a system-level
solution that mitigates the effect of this issue when an occasional Ethernet boot is
required. In the example described above, the system could be designed with the boot
sequence defined by SYSBOOT [4:0] = 11001b which attempts to boot from MMC0
before Ethernet. This does not provide a default method to break into the boot sequence
with Ethernet boot, but the product could be designed with a switch that temporarily
disables MMC0 boot as a way to invoke Ethernet boot. The switch would only be used to
temporarily disable MMC0 while the product boots from Ethernet. Once the product has
booted from Ethernet, the switch would be returned to its normal operating mode before
the MMC0 boot code is updated.
27
SPRZ360F – October 2011 – Revised November 2013
Sitara™ AM335x ARM
®
Cortex™-A8 Microprocessors (MPUs) (Silicon
Revision 2.1, 2.0, 1.0)
Copyright © 2011–2013, Texas Instruments Incorporated