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LDmicro Forum - PIC16F876

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PIC16F876 (by segar)
PIC16F867 (by segar)
Hi, this is important massage for all who ever use MCU PIC16F876
Please carefull, The pin 6 RA4/TOCKI INPUT OR OUTPU ITS NOT WORKS IN LDMICRO,V2.2/V2.3/V4.0/V4.1.1/4.1.2 DONT HAVE OUTPUT AFTER PROGRAM IN TO CHIP THE HEX FILE.

I HAS BEEN TEST MANY TIMES AND ANALYSE FEW TIMES IN THE PROGRAM I DONE THE ATTACHMENTS ITS BELOW MY PROGRAM IN LDMICRO. ITS SIMPLE PROGRAM I WRITE AND TEST ITS NOT WORKS. I AM USING MICROCHIP PIC- KIT2 PROGRAMMER AND ALSO WELLON VP-996 PROGRAMMER
ITS SAME NOT WORKS. AND I TEST OTHER ALL THE PIN IN PIC16F876 ITS WORKING WELL NO ANY PROBLEM OR ERROR ,ONLY THIS MCU PIN6 RA4/TOCKI PLEASE IF ANY ONE HAVE TEST THIS PIN LET ME KNOW THE FEED BACK.

THANKS
Wed Jan 11 2017, 21:22:06, download attachment PIC16F876 MCU PIN6 TEST PROG.ld
(no subject) (by MGP)
I always use the 16F876a and never had problems.
Pin 6 works for 100% every time.

If you look at the datasheet you can read that pin6 is OPEN DRAIN and for output you need a extra resistor.

As input it acts as all the other inputs.
Thu Jan 12 2017, 02:02:23
(no subject) (by Ihor Nehrutsa)
page 29:
...
The RA4/T0CKI pin is a Schmitt Trigger input and an open drain output.
All other PORTA pins have TTL input levels and full
CMOS output drivers.
...

FIGURE 3-1 and FIGURE 3-2 shows difference between the pins.

page 31:
...
Each of the PORTB pins has a weak internal pull-up.
...

etc. etc.
Thu Jan 12 2017, 02:36:35, download attachment PIC16F873_874_876_877.pdf
(no subject) (by Ihor Nehrutsa)
Choosing an Appropriate Pull-up Pull-down Resistor for
Open Drain Outputs
PIC16F876 (by segar)
HI, problem i facing is no output in pin6 ,i have use pull-down resistor as what show in the datasheet, for PIC16F876 is problem ,for the PIC16F876A is no problem. please make sure this issues ,i am trying to check in the fuse setting also its same problem

i am using crystal 4.0MHZ for PIC16F876 ,ITS NOT WORK OUTPUT

please note.
Fri Jan 13 2017, 04:53:55
(no subject) (by MGP)
For output, you need a pull-up resistor for both the F877 as an F877a.

You have two options, either the pic failure or you make a mistake in the hardware, it is certainly not LDmicro.

We can not invent something wrong that should work.

Do you have a schematic of your circuit?
Fri Jan 13 2017, 05:38:22
(no subject) (by Boris)
Pin 6 doesn't give You 5V as output it only switches GND
(when output is ON You have GND for output)
If You use pull down resistor You will have always GND on output.
If You need +5V on output use pull up and invert logic for that pin.
Change pin it is easiest way to solve problem.
Fri Jan 13 2017, 15:49:53
PIC16F876 (by segar)
hi, boris you talking about only pin6 need to pull-up or other pin all have to pull-up? the program i use at same chip MCU others all its working output 5v same program i write as well.

thanks
Fri Jan 13 2017, 19:48:27
(no subject) (by MGP)
Segar, only pin 6 has an open drain output, everything else has a push-pull output.
Even in a 16F628A is RA4 open drain and also in many other pic's.

This is ingrained in the chip and you can not change that, not even with software.
That this works on other chips is not true, you are lucky that the following circuit changes state when no signal is connected.

Put some effort and search the internet on the difference between open-drain (open collector) output and push-pull output, there are millions of articles on the internet about it.

Again, your program has nothing to do with this, it is hardware related.
Sat Jan 14 2017, 03:08:30
PIC16F876 (by segar)
HI,MGP
i really appreciate you reply me and advice, any how i have attachments for my circuits as you mentioned problem in my hadrware,so please have look the attachments of my circuits.


thank you
Sat Jan 14 2017, 04:27:32, download attachment PIC16F876.docx
(no subject) (by MGP)
Here you have the solution.

Invert the output in your program, else 1 = led out and zero = led on
Sat Jan 14 2017, 04:49:08, download attachment Snap215.jpg
pic16f876 (by segar )
hi,

any how thank for reply as well , but your solution is not works

i will do my own thank you again .

thank you
Tue Jan 17 2017, 05:56:56
(no subject) (by Boris)
ONLY FOR PIN6 use PNP transistor where resistor R27 goes to +5V.
If You want to switch Gnd then Gnd is connected to Colector
If You want to switch +V then +V is connected to Emiter.



I think that something is wrong with your drawings because on both sides of LED is GND
Tue Jan 17 2017, 14:33:45
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