What types of AT commands we are required to send to start communication in API mode?

Can I also have to configure the XBee connected to controller as Coordinator ??
AT commands are used to read and write the setting of XBee or to change it. So what types of command I send so that it starts communicating?

Is the communication Ok if we configure one XBee in AT mode and one in API mode?

Abhinav,

First, yes, you can mix AT and API mode nodes without a problem.

Next, if the module is in API mode (ATAP1 or 2), then all you need to do is issue the TX API frame with the proper data. Then the XBee will send it to the node in its network that has a matching address.