can someone explain me what is the theory behind JDM programmer? and how it differ from other programmers?
thank you

 

This Programmer is powered by the RS-232 and it works with RS-232 levels at only < ±8.6V. It programs PIC12C5XX, 12C67X, 24CXX, 16C55X, 16C61, 16C62X, 16C71, 16C71X, 16C8X, 16F8X and ISO-CARD's with ASF.

see:
http://www.jdm.homepage.dk/newpic.htm

 

This Programmer is powered by the RS-232 and it works with RS-232 levels at only < ±8.6V.

It should be ">" +/- 8.6V.

There are so many "problems" related to the JDM programmer design which does not do it justice. Many people then conclude it is a bad circuit design.

It was a proper design which works with standard RS232 port implementation. What this means is the signals on the RS232 port lines must swing from -8V to +8V or more, as the PIC programming voltage and chip power are all derived from these signals alone.

Simplest to say: If your RS232 port cannot output these voltage levels, then JDM programmer will not work reliably. Most if not all "old" desktops with parallel and serial(COM) ports and no USB meet this requirement and JDM works beautifully. Sadly, most COM port on laptops or USB-serial converters cannot. One needs to check and confirm.

Use a DVM to measure the voltages on all the pins of the serial port with respect to ground. If you get +8V, -8V or more, then the JDM design will work.

The JDM has served me well over the years.

 

actually i'm more concern about theory of operation

 

is there any existing jdm programmer that is working with a usb to rs232 comverter?, the target is PIC16F84A chip??,thanks in advance...

 

is there any existing jdm programmer that is working with a usb to rs232 comverter?, the target is PIC16F84A chip??,thanks in advance...

i dont think there is

 

If you have acces to a +/- 12 volt power supply I guess you can buy some cheap RS232 interface circuit like the SN75C185N and use it to "amplify" the RS232 signals. I guess the critical signal is the DTR and RTS signals. Just a tip