Error while trying to enter sleep mode


While trying to enter sleep mode on beaglebone black am getting an error

When i issue the command echo -n “mem” > /sys/power/state am getting -sh: echo: write error: No such device

The kernel version and os version is as below

root@beaglebone:~# uname -a
Linux beaglebone 3.8.13 #1 SMP Wed Sep 4 09:09:32 CEST 2013 armv7l GNU/Linux
root@beaglebone:~# lsb_release -a
Distributor ID: Angstrom
Description: Angstrom GNU/Linux v2012.12 (Core edition)
Release: v2012.12
Codename: Core edition