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Whats wrong when multimeter beeps between Vdd & Vss on 8

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brmadhukar

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Wasted PICs

Hi,

I find the multimeter "beeps" between Vdd and Vss on 877A. Does it indicate PIC is bad.

This may be due to mistake in programmer board.

In Peatman's book there a statement saying only 5 pins are needed for programming. There are 2 Vdd and 2 Vss pins.

TIA
BRMadhukar
 

Re: Wasted PICs

Vdd and Vss shorting is only bad if the PIC is out of circuit. In circuit, this can be due to a number of things.

On PICs that have multiple Vdd and Vss pins, they should all be connected (in theory). However, you can most likely get away with just connecting one set since they are connected internally.

Yes you only need 5 pins: RB6, RB7, MCLR, Vdd, and Vss I believe.
 

Wasted PICs

If the PIC is mounted in circuit you have beep because the capacitors between VDD & VSS.

Out of circuit or if you don't have mounted bypass capacitors the PIC is probably broken.

For programming:
RB7- Data
RB8 - Clock
MCLR- Master clear/VPP
VDD
VSS
 

Wasted PICs

Capacitors are not shorts!


ASIC
 

Re: Wasted PICs

2 Vdd and 2 Vss is for the facility of layout design. You may use either of them according to your pcb layout. If you can use every of them this the ideal. Because if one Vdd gets damaged then the other can funciton.
 

Re: Wasted PICs

atmaca said:
2 Vdd and 2 Vss is for the facility of layout design.
Click to expand...
NO, this is for sharing current between 2 pins, when PIC has many IO
If the PIC doesnt provide a huge ammount of current to the rest of the app, then its not necessary to connect all of them. on the contrary you have to connect all Vdd and Vss pins (or the PIC may be dammaged)
 

Re: Wasted PICs

Hi,

I am using a Oshon PIC programmer. I tried programming two pics y'day. Both of them failed at 0x0006 location. I am unable to erase it. Can I just use Goto to bypass this location.
TIA
BRMadhukar
 

Wasted PICs

Hi,

You should not skip that location! That indicates
the programming process was bad (wait timing,
programming voltage etc), and therefore that
memory location wasn't properly programmed
and readed back.
Use EPIC programmer, it's cheap and working.
You can find it's schematics in this forum.

good luck,
Zed
 

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