Author Topic: Help identifying an ST IC.  (Read 770 times)

0 Members and 1 Guest are viewing this topic.

Offline gkmaia

  • Frequent Contributor
  • **
  • Posts: 413
  • Country: nz
  • Electronics Hobbyist
Help identifying an ST IC.
« on: August 19, 2019, 02:33:52 am »
I got a keyboard with a faulty PCB and have been trying to figure out what IC is this one. If it is a processor, gate array or what... but cannot find a datasheet anywhere.
 

Offline fzabkar

  • Frequent Contributor
  • **
  • Posts: 522
  • Country: au
Re: Help identifying an ST IC.
« Reply #1 on: August 19, 2019, 04:24:21 am »
 
The following users thanked this post: gkmaia

Offline gkmaia

  • Frequent Contributor
  • **
  • Posts: 413
  • Country: nz
  • Electronics Hobbyist
Re: Help identifying an ST IC.
« Reply #2 on: August 19, 2019, 06:10:44 am »
Exactly it. From an mAudio board. Thanks for that.

The dream SAM9708 is the DSP. Feels like the ST could be processor as it has crystal beside it. Would be good to have a datasheet to test some of the pins.

There is an implementation of the same DSP that uses the same memory setup here

https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQ272wPem32-LuGsEk-7yJt0wdYh9lrOmAl_iXHn5TgrtaHudPg

I can get clock out of pin 91 so I believe its internal oscillator is working. But apart from that no other pulse. It could be fried of stuck on HALT or RESET. I am not sure... need to investigate more.
« Last Edit: August 19, 2019, 10:10:02 pm by gkmaia »
 

Offline gkmaia

  • Frequent Contributor
  • **
  • Posts: 413
  • Country: nz
  • Electronics Hobbyist
Re: Help identifying an ST IC.
« Reply #3 on: August 19, 2019, 08:57:30 pm »
The DSP is held in RESET by ST PI12.

When I bypassed the RESET so I would not go LOW the DSP booted up and there was activity on the memory busses and on the op amps.

The ST PI12 seems dead. The only activity I get out of it is it's oscillator running the crystal at 8MHZ.

But that is all. Did a bit of research on ST micro-controllers but could not find anything that could match what would supposedly be the VCC & VSS.

« Last Edit: August 20, 2019, 09:10:24 am by gkmaia »
 

Offline fzabkar

  • Frequent Contributor
  • **
  • Posts: 522
  • Country: au
 

Offline gkmaia

  • Frequent Contributor
  • **
  • Posts: 413
  • Country: nz
  • Electronics Hobbyist
Re: Help identifying an ST IC.
« Reply #5 on: August 23, 2019, 02:53:37 pm »
Yes it is. Have you been working on this board as well?
 

Offline fzabkar

  • Frequent Contributor
  • **
  • Posts: 522
  • Country: au
Re: Help identifying an ST IC.
« Reply #6 on: August 23, 2019, 06:06:36 pm »
Yes it is. Have you been working on this board as well?

No, I've just taken an interest in your thread.
 
The following users thanked this post: gkmaia

Offline magic

  • Super Contributor
  • ***
  • Posts: 1812
  • Country: pl
Re: Help identifying an ST IC.
« Reply #7 on: August 23, 2019, 07:40:43 pm »
Check supply rails and electrolytics.

If it's some oldschool MCU, one capacitor may implement an RC delay circuit resetting it on power up. Those things sometimes go bad.
 

Offline gkmaia

  • Frequent Contributor
  • **
  • Posts: 413
  • Country: nz
  • Electronics Hobbyist
Re: Help identifying an ST IC.
« Reply #8 on: August 23, 2019, 10:27:55 pm »
I ended up implementing it like that. The cap is 20uf and it takes around a 1 sec to charge up and bring the RESET threshold to HIGH. Probably a 10uf would reduce the time but I do not have one here.

Anyway it works fine. Only bad side is if the rail goes up there is nothing to turn the IC off anymore.

But was a nice little trick anyway!
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf