You are on about a PICAXE
www.picaxe.co.uk i think.
They are good for quick prototyping, but painfully slow and very limited on features / program space. Ideal for schools really.
They have a programming enviroment called Programming Editor which has a BASIC and Flow Chart editor for creating your programs (you can use either flow chart or basic, but u can convert a flow chart to basic but not the other way round unfortunatly).
The Programming is done via the COM ports using a stereo plug/socket. (these plugs and sockets are quite a good idea even for normal PICs as u dont need to use a full size D socket
although there is one grounding problem as the ground part of the plug is the tip, but i have never had trouble).
The socket then uses a pull down (10K) and current limiting registor (22K) on the RX to the PIC (the TX From the computer) and a direct line to the RX of the computer from the TX of the PIC. I do not have much of an idea what this does, but i know it creates a +5V to 0V output which is inverted or somming.
The PICAXE itself has a firmware program on it which downloads the program (a tokenised series of instructions for those of you who care) and stores it on the PIC, i think it uses the program space.
It is a nice system to use when you need something working quickly with kids or even if you dont want to bother with assembler / PIC Programmers and alike. I know there have been some interesting projects with it, even had one online at one point.
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Just as a side note, i would suggest you get more into bootloaders that the above type of PIC use. I use the bootloader that you can get from
www.sparkfun.com and it is great (for the 16F877A/876A/873A/88) i am using 2 pics in my current project and both have the bootloader on them. I have a max232 connected to each PIC, the 16F873A uses a normal D connector and the 16F877A uses the PICAXE cable / stereo socket connected to the MAX232 and i have both connected to my PC's COM ports.
I have 2 instances of the downloader program running and when i need to download an update i close the hyperterminal for that pics COM port and then click download, hit the PICs reset pin and the download takes place.
I use the downloader at 115200 kbps so it is faster that a normal PIC programmer, expecially when you take into account the removal of the PIC from the circuit to do so.
Regards,
- Martyn