IN CIRCUIT PROGRAMMING.

This circuit was incorporated into BugBots main board to make development much easier.

However if you already have a PIC16F84 compatible programmer and have to place the target PIC into the programmer for programming then this will also work for you! All you have to do is take into consideration the points below when designing your next project.

If you have any queries you can contact  me at: enquiries@zibot.co.uk

Circuit Description:

In order for the in-circuit programmer to function correctly the supply must be disconnect from the target board! This is necessary as the programmer needs to control the +5V line to the target PIC.

This design is the one used on BugBots main board and is just one suggested method.

You will need to make up a lead to connect from your PIC programmer to the header on the target PCB.

To program the PIC just switch of the board, connect the header and use your programmer as normal.

Vdd is the +5V supply from the programmer.
As it is highly unlikely that your programmer will be able to power all but the target PIC, it is necessary to block the +5V supply from the programmer to the rest of your circuit. This is achieved with D1.
Note: When the PIC is supplied normally with a +5V supply the supply will drop by approx 0.6 Volts. The PIC16F84 will happily operate at 4.4 Volts. 

Vpp is the programming pulse from the programmer, this raises pin !MCLR (pin 4) to +13.5V and puts the PIC16F84 into programming mode.
As !MCLR needs to be connected to +5V in order for the power on timer to function correctly during normal operation. R1 is used to isolate the programming voltage from the +5V supply during programming.

Gnd is the common ground connection between programmer and the target PCB.

Clock is the timing signal from the programmer and Clocks the Data in and out of the target PIC.

Data is the pin on which the data is carried to / from the target PIC.

Note: Due to the dual function of pin13 and 14 on the PIC it is necessary to take into consideration what function IO pins RB6 and RB7 have on your PCB. It may be necessary to isolate them from the programmer. In Bugbot's case these pins are used as inputs and thus a 2K0 resistor is used to isolate the programmer from the rest of the Circuit.  However if you don't need the extra I/O's then leave these pins dedicated to the programmer.

 

PIC16F84 In-Circuit Serial Programming lead (home made) and Picstart Plus programmer from Microchip (TM)

I just soldered a couple of rows of pins onto a bit of veroboard soldered the connector on the other end. Plugged the veroboard into the programmer as if it were the PIC itself and hey presto on in-circuit programmer. No more having to remove the IC from the target board (or bread board for that matter and plugging it directly into the programmer.

It knocks hours off your development time especially if you trying to nail down a nasty little software bug!
 

 

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