ICSP using a 16F84a to program 24CXX

[skimask]

Hi - no you are not missing anything. Only thing is my poor way of asking question.

Ok...I think I might be getting the picture.
Do you have a method to program a 24xxx chip right now?

[aftab]

Ok...I think I might be getting the picture.
Do you have a method to program a 24xxx chip right now?

Yes.
Now I program the 24 using Olimex JDM programmer:
http://www.olimex.com/dev/index.html

Using the ICSP header I connect them as:
http://www.olimex.com/dev/images/pic-icsp.gif
3-Gnd-->gnd of 24CX
4-PGD-->Data of 24CX
5-PGC-->Clk of 24CX

Using windows Pic progarmming software, I can program the 24X

But not by 16f84a.
Could this be a voltage issue ? or Should I try something else than i2cwrite ?

Thanks
Aftab.

[mister_e]

SDA and SCL pin must be pull-up with resistors... as in the manual.

The code example in the manual should work AS-IS

[skimask]

SDA and SCL pin must be pull-up with resistors... as in the manual.

The code example in the manual should work AS-IS

I was just going to say that...along with adding an active pulldown on WP. Datasheet says there's an internal weak pull down, but ya never know.
(BTW - Now I get what you're getting at).

[aftab]

SDA and SCL pin must be pull-up with resistors... as in the manual.

The code example in the manual should work AS-IS

I think I tried that last night - but could have done wrong.
But when I had placed a 24C on my breadboard - it worked.
But when I got 3 connectors to the circuit board with 24C on it, it did not work. However, I shall try that tonight once my classes are over.

But I may sound stupid - till now I do not understand what pull-up means. I shall attach the 4.7k resistors (or other value ?). Only know that resistors are needed to pull-up(?) to program i2c.

Shall post my result of this.

Thanks
Aftab.

[skimask]

I think I tried that last night - but could have done wrong.
But when I had placed a 24C on my breadboard - it worked.
But when I got 3 connectors to the circuit board with 24C on it, it did not work. However, I shall try that tonight once my classes are over.

But I may sound stupid - till now I do not understand what pull-up means. I shall attach the 4.7k resistors (or other value ?). Only know that resistors are needed to pull-up(?) to program i2c.

Shall post my result of this.

Thanks
Aftab.

Pull up....
On signal lines that can be connected to more than one device (in this case I2C's SCK and SDA), the signals aren't powered directly by any of the chips, but by power and the pullup resistors. The various devices can only apply a ground to the signal line. If no devices on the bus are applying a ground, the line stays high (logic 1, at near power supply voltage). If there are multiple devices on the bus, and any one of them applies a ground, the entire signal line drops to ground (logic 0).

If you had each chip holding the signal lines high, and one of them tried to make the signal line a low (logic 0), the other chips would either overpower it, or you'd end up with a lot of smoke in the room

Same thing goes for a pull down, but the other way in reverse.

Most of the time, the terms 'pullup' and 'pulldown' aren't so complicated. A pullup just means a high-ish value (4.7K, 10K, etc) resistor between Pin X (or whatever) and the positive supply rail. Conversely for the pull down, a resistor between Pin X and the ground rail.

[aftab]

Pull up....
On signal lines that can be connected to more than one device (in this case I2C's SCK and SDA), the signals aren't powered directly by any of the chips, but by power and the pullup resistors. The various devices can only apply a ground to the signal line. If no devices on the bus are applying a ground, the line stays high (logic 1, at near power supply voltage). If there are multiple devices on the bus, and any one of them applies a ground, the entire signal line drops to ground (logic 0).

If you had each chip holding the signal lines high, and one of them tried to make the signal line a low (logic 0), the other chips would either overpower it, or you'd end up with a lot of smoke in the room

Same thing goes for a pull down, but the other way in reverse.

Most of the time, the terms 'pullup' and 'pulldown' aren't so complicated. A pullup just means a high-ish value (4.7K, 10K, etc) resistor between Pin X (or whatever) and the positive supply rail. Conversely for the pull down, a resistor between Pin X and the ground rail.

That was great !

[skimask]

That was great !

Jeeze...finally. I've been a bit off on explanations/corrections/help/etc for a few weeks now. It's about time I got something right. (my 'lab' is under reconstruction due to exterior water intrusion, read that as flooded out...I haven't programmed a PIC in over 2 months!!!). I think I'm suffering from withdrawl...

Anyways...get those resistors fitted and let us know what happens...