GSM Sim900a test

it seems that the program restart again again.I mean arduino behaves like, it is automatically reset itself again again.what is the reason of it?i check power and reset button through different program and it is okay.only for this program it behaves like this.Below here i attached a photo.It will be very helpful if anyone tell me the reason of it.

#include <SoftwareSerial.h>
SoftwareSerial mamun(2, 3); //RX is in 2, TX is in 3
int inByte = 0;
void setup()
mamun.begin(9600); // GSM baud rate

Serial.print(“Command start:\n\n”);

mamun.println(“AT+CMGDA=“DEL READ””); //for delet all SMS
mamun.println(“AT+CMGF=1\r”); //Set SMS Text Mode
void loop()
{Serial.print("."); //here i use “.” to understand the output behavior
if(mamun.available() >0){
inByte =;


Serial Output:
…Command start:

.A.T.+.C.M.G.D.A.=.".D.E.L. .R.E.A.D.".

it seems that the program restart again again.

But only prints "Command start" once? Not likely.

Is the Program Resting or the GSM because if you don't have the power the gsm wont work it will keep resetting also depends in the capacitor at the gsm module.. and why are you using SIM900A???? it will only work in Asia if that's where u are.. SIM900 is a better module and its quad band... the Sim900A is only 2 Band..