Vpp

chrys0720003 · ‎2002-10-21

Posted on October 21, 2002 at 21:48

Vpp

chrys0720003 · ‎2002-09-25

Posted on September 25, 2002 at 13:34

Hello,

I am checking my hardware and have a few questions regarding the consequences of short circuit/broken wires:

What can happen if Vpp is floating?

What can happen in case of a short between Vpp (lets imagine Vpp is not connected to ground) and the Reset pin (neighbours on the TQFP32 type)?

Are the potential consequences the same for FLASH and ROM devices?

Thank you

Tane

vialclaude · ‎2002-09-25

Posted on September 26, 2002 at 06:08

Hello!

Here are a few explanations in order to answer you:

Necessary condition for the Vpp is to be tied to proper pin when you program the device. For the programming purpose in both cases (Vpp floats or short to any pin), user cannot program the device. If Vpp is not connected to the proper pin, which supplies the programming voltage to device, device will not allow to program the memory. When you run the application, this pin should be tied to low level.

If Vpp is floating, behaviour cannot be predicted. If voltage is low level, chip will work fine. If it reaches the high level at the time of power ON, it will not run the application. If Vpp is short to any pin. It will not affect chip application when power ON, chip works fine. But once you power OFF and ON again and if short pin is active high at the power ON, This will not satisfy the start condition for the Vpp logic(low level). So this will not allow device to run application. (In case of RESET, it is active low for 324 device. It is with high level at the time of power ON. This will not allow device to run an application).

If Vpp pin is for programming and mode selection for the device, this observation will be there for that device and of course for both ROM and FLASH.

Regards.

maxime2399 · ‎2002-10-03

Posted on October 03, 2002 at 21:36

In case you short the Vpp and another pin while the 12V is present, there is a big chance to destroy the device too!

It's always safer to remove the 12V when not programming.

johan239955_stm1_stmicro · ‎2002-10-21

Posted on October 21, 2002 at 21:48

Talking about Vpp, make sure that Vdd is between 4.5V and 5.5V before applying your 12V on the Vpp pin (check power up and power down). Otherwise you may stress the Vpp pin and damage your micro.

Regards,

Jojo