PIC10F microcontroller output pin tolerance to overriding voltages

I am using PIC10F microcontrollers in a wireless project that has evolved into needing to use an 'in circuit' programmable radio IC.

The problem is that the GP2 pin of the PIC would be connected to the DATA input (and programming) pin3 of the radio IC.
The whole circuit is running off 3v7 lipo battery.
My question is will the PIC GP2 output be destroyed when programming the radio IC. ?

Thanks in anticipation....

Dave

Top Replies

michaelkellett over 1 year ago in reply to davebullockmbe +2

You can set GP2 as an input to prevent it from loading the radio pin during programming: From the Microchip data sheet. 5.2 TRIS Registers The Output Driver Control register is loaded with the contents…

0 JWx over 1 year ago

maybe some OR gate could be placed between if external programming is needed? Or even removable jumper - even if GP2 will not be destroyed by forcing it into opposite state, it could interfere with programming signal...
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0 dougw over 1 year ago

Could you use a Schottky diode in series to protect the PIC?
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0 davebullockmbe over 1 year ago in reply to dougw

HI thanks for your considered replies. I had thought about a jumper but board space is too tight. Maybe I can make room for a 0402 schottky diode though. I was hoping I would get away without reworking the board but you have confirmed my doubts. Thanks Dave
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0 dougw over 1 year ago in reply to davebullockmbe

You might also need a pull down resistor unless you can just short out D2.
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0 dougw over 1 year ago in reply to davebullockmbe

Actually, you could replace R6 with a diode and D2 with a resistor. Then you would just need a jumper to the data pin (and a cut to the original path).
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0 scottiebabe over 1 year ago

If you could hold the processor in reset, GP2 would be tri-stated...
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0 davebullockmbe over 1 year ago in reply to scottiebabe

Yes the problem with adding a diode in series with the data line is as you say the data pin of the radio chip will float and so need a resistor to pull it down. Unlike Microchip datasheets I cannot find any information about the internal structure of these radio IC's ie. whether they have internal pull-ups/downs. I have just about run out of board space and am struggling to add even one more component.
However putting the PIC10F202 into reset would be a great idea but doesn't this need extra PIC code to force the o/p pins into tristate. I don't think toggling MCLR does this on it's own?
Dave
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0 michaelkellett over 1 year ago in reply to davebullockmbe

You can set GP2 as an input to prevent it from loading the radio pin during programming:

From the Microchip data sheet.

5.2 TRIS Registers
The Output Driver Control register is loaded with the
contents of the W register by executing the TRIS f
instruction. A ‘1’ from a TRIS register bit puts the corresponding
output driver in a High-impedance mode. A
‘0’ puts the contents of the output data latch on the
selected pins, enabling the output buffer. The exceptions
are GP3, which is input only and the GP2/T0CKI/
COUT/FOSC4 pin, which may be controlled by various
registers. See Table 5-1

MK
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