Could anyone please tell , what are the software serial support pins of ATMEGA 1284P.
The whole point of software serial is that it works on any pins with a PCINT. In the case of the '1284p, that's any pin.
It also sucks, and should be avoided whenever possible, particularly receiving, and particularly in demanding applications. It can't receive and transmit at the same time, it blocks, and it disables interrupts while sending and receiving.
The 1284p has TWO hardware serial ports. Serial is the one normally used for the bootloader, and connected to the serial monitor, it's on arduino pins 0 and 1 (bobuino pinout, 8 and 9 by the other one, PD0, PD1, physical pins 14,15). You may need to disconnect stuff from these pins while uploading, though. Serial1 is not used by anything (normally) and thus is free for you to do whatever you want with. It's on arduino pins 2 and 3 (bobuino pinout, 10 and 11 by the other one) PD2 and PD3, physical pins 16,17, right next to Serial. You use Serial1 just like Serial (ie, with Serial1.begin(), Serial1.print() etc). Use the two hardware serial ports, and only resort to SoftwareSerial if you absolutely have to.
Thanks ....very much for your advice... 