The Philips bootloader can be considered half-duplex as long as you wait for the echo each time you transmit a single character and then provide adequate time for operation results to be transmitted back.

Flash Magic has an option to enable half-duplex communications like this, although it does slow down the programming time.

If you wish to use RTS, XON, etc. then your only option is to write your own bootloader as they are not supported by the Philips bootloader. However, on our web site www.esacademy.com in the technical library there is a C library for using the IAP - In Application Programming - features of the Philips Rx2 and 66x (the 669 will be added in the next few days), which you can freely download. This makes it a lot easier to write your own bootloader as it takes care of the actual flash programming side of things. All you need to implement is your serial protocol. Obviously, if you stray from the Philips serial protocol, then you will need to write your own ISP program as well for the PC end.

However, isn't it is possible to implement RS485 without needing RTS, etc? Erik will know more about that I'm sure. I personally have not tried it.

Andy
Embedded Systems Academy
www.esacademy.com