Yes, you're right about the builtin bootloader. You must also force a few pins on the device to enter bootloader execution mode; this is what the 74xx125 tri-state buffers shown in Dallas' documentation are for. And yes, you do just load up standard Intel Hex files over the serial port; the bootloader takes care of all the parsing and decoding for you. It should be possible to do the downloading with standard terminal software. However, if you use standard terminal software, be sure to pay attention to the responses from the device to ensure that your programming is succeeding as expected. Still, there are not a whole lot of reasons to use standard terminal software when freely available special-purpose programming utilities for these devices exist, such as Dallas' MTK and my own 89C4x0ldr-lite, unless you are on an unsupported platform. The former offers a user-friendly GUI, while the latter offers a simple, scriptable CLI.


Well, it's a nice device. If you can run it at moderate frequencies, it's quite manageable, and can still outperform a lot of more conventional 8051-based devices. But, as you head for the upper range of clock speeds, you start running into issues. An LS address latch is no longer sufficient. Stretch cycles become necessary to interface with many peripherals. Noise shows up on ALE. And the list goes on.

Note that none of this is to say the device is inappropriate for students and hobbyists, but I think it would be a daunting challenge for a first expierience with microcontrollers without someone providing a good amount of hand-holding.

--Sasha Jevtic