Datasheet

VIPER / VIPER-Lite Embedded Linux Development Kit Quickstart RedBoot

The only difference is that the default boot script initializes the clock to 400MHz for

VIPER and to 200MHz for VIPER-Lite. Refer to following section for more details on

‘clock’ command.

%{FREEMEMLO} is a predefined alias for the lowest address of available memory.

%{kernel} is an alias for the full path name of the Linux kernel to boot. For example:

Redboot> alias kernel “-f /boot/bzImage”

%{cmdline} is an alias for the kernel command line to use. For example:

Redboot> alias cmdline “\”root=/dev/mtdblock2 rootfstype=jffs2 ro

console=ttyS0,115200\””

Refer to the AEL Technical Manual for further details.

CPU core clock frequency and the clock command

Redboot (V3I7) does not change the clock rate - it remains at the default 100MHz

setting. However, the clock command can be used to set the clock to any of the

frequencies described in the section CPU clock frequency scaling

on page 22. This

takes parameters l, m and n correspondingly for the L, M and N settings, which control

the clock speed as described.

While specifying on Redboot command-line, the value of n should be 10 times the

desired value of N, i.e. to set N to 1.5 use the option -n 15. For example:

To set the clock frequency to 300MHz power saving mode: •

•

RedBoot> clock –l 27 –m 1 –n 30

To set the clock frequency to 200MHz performance mode:

RedBoot> clock –l 27 –m 2 –n 10

Attempting to run a VIPER-Lite board above 200MHz or a VIPER board

above 400MHz may damage your board permanently.