How can i communicate between two C6713 boards

HPI is the highest bandwidth path of these choices, but it is a master-slave interface. The Master DSP will connect its EMIF to the HPI port of the slave DSP. I suppose you could do the same connection both ways, assuming the pins are available for both EMIF and HPI. I believe there are application notes that discuss this type of connection, but definitely there are examples of connecting the memory bus from one processor with the HPI of a DSP. Please search for those if you wish to implement this method. You will want to search this forum, the TI Wiki Pages, and certainly the Product Folder at TMS320C6713B.

The McASP is a multi-port version of the McBSP. Each channel can deliver serial data at the speed stated in the datasheet, usually 10 or 50 or 100 MHz. The McBSP has a transmit port and a receive port, and both of these can operate simultaneously. The McBSP is the simplest method to communicate between two DSPs, in my opinion. The McASP can provide more total bandwidth by using multiple serializers or channels.

GPIO is a very inefficient method of sending data. GPIOs can be used effectively for signalling, and they can be used to implement a specific hardware protocol at the expense of DSP MIPS. But for basic data communication, the McBSP would be much better. A comination might be effective, using a GPIO to signal that communication should start or has ended, for example. But even that might not be needed with the McBSP.

You will generally get better responses on the forum by starting a new thread, rather than adding an unrelated question to a thread that has been answered. It may help you get the most out of the E2E forum if you have some time to review the Getting Started information here.

Regards,
RandyP