I know that ATmega328 can interface with a physical serial port using a chip like MAX232. I have built such a circuit and have verified that I could send data and receive data via the serial port.
But my question is, does the current version of Arduino bootloader support program loading (e.g. through Arduino IDE) via the physical serial port (e.g. COM1)? The reason I am asking is that when I tried it didn't work and I didn't observe any activity on either the TX or RX line using an oscilloscope. But as I stated earlier, if I use Serial.read() and Serial.write() I could interact via a terminal directly. So I know that the circuit is working properly.