I want to connect an ATmega162 with a sony-ericsson GM29 GSM modem(AVR as DTE). The problem is that the modem has hardware flow control on its RS232 port enabled by default, and I have trouble implementing hardware flow control an the AVR side. What I have tried so far is pulling the RTS line low, and wait CTS line (connected to INT0) to trigger an interrupt. Then allow the program to send a byte and pull RTS line high again. Is this right? Any help would be greatly appreciated.