I am testing the sim900 at commands in Hyper terminal.Its works properly wants to implement my program.

I am able to ready the sms by using at+cmgr=sms number
eg:at+cmgr=8 which upon displays sms details. If i want to see the sms that has sent immediately,before even typing the command in typerterminal ..i'm getting +CPIN not after any at command that i enter will return error only...

Kindly let me know whta could be the problem.Right now am checking the sim900 through USB cable not through serial cable.

One more doubt i want to clear at+cfun=1 is same as reset modem..but it doesnt show any call ready message.when i do unplug and plug the power supply then only it shows

+CPIN Ready

call Ready ....then only i command at+cmgr works...? is there any alternative forreset instead of removing the power supply again and new to this technology...if it is a silly question....kindly consider as a mewbie person and pls reply....