How a micro-controller programmer works

Hi,

Could someone describe to me how a microcontroller programmer can program
a microchip, using RS232 signals. Taking a simple JDM programmer to
program a PIC16C84, I don't understand how RTS and CTS signals, which are
onnected to data and clock pins (RB6 and RB7, if I am right!) can send
program to the chip. I am confused ! I wanted to simulate the JDM circuit
(using PSPice) to figure how the circuit functions, but I don't know how I
should simulate the RS232. Could you please help me understand how
programmer works. 

Thanks   
Nader

> Could someone describe to me how a microcontroller programmer can program
> a microchip, using RS232 signals. Taking a simple JDM programmer to
> program a PIC16C84, I don't understand how RTS and CTS signals, which are
> onnected to data and clock pins (RB6 and RB7, if I am right!) can send
> program to the chip. I am confused !

Not familiar with this specific product, but RTS and CTS are control
rather than data signals for the serial port, which can probably be set
under software control.

What it sounds like they are doing is not using the serial port for
it's designed asynchronous serial function at all, but rather using it
just to get two software controlled bits to bit-bang a synchronous
(data and seperate clock) serial signal that the PIC may more easily
handle - it's not RS232.

>From the sound of it you could probably do the same thing using two
bits of a parallel port.

Unless the serial txd and rxd signals are also connected to something -
if that's so, then disregard this post.

cs_posting@hotmail.com wrote:

[...]
> Unless the serial txd and rxd signals are also connected to something -
> if that's so, then disregard this post.

You can also toggle TxD manually by using the break-condition.

/Jan-Hinnerk