STPC Atlas Strap options

jalonso1 · ‎2007-03-06

Posted on March 06, 2007 at 10:56

jalonso1 · ‎2006-12-05

Posted on December 05, 2006 at 10:42

Hello,

We are using STPC Atlas and trying to configure it in DX1 mode, with MCLKO and HCLK pins configured as outputs. Being so, we have added 470K pullups to MD14, MD18, and MD19 signals. However, corresponding bits of strap registers are 0 for these options. In the other hand, HCLK and MCLK pins are really behaving like outputs, which do not match with strap registers.

Remaining strap options are correctly shown in strap registers. The fact is we are having some inestability issues and are worried about MD14 being 0 in the strap register.

Could anyone explain this strange behaviour and help us?

Thanks anyway.

kaouther · ‎2006-12-05

Posted on December 05, 2006 at 13:22

Hello,

To select the CPU clock multiplication, you need to configure MD14 & MD40. MD14 is pulled up set to 1. In X1 mode, MD40 is set to 0 ''pulled down'' and in X2 mode MD40 should be set to 1 ''pulled up''. So, in both modes X1 & X2, the MD14 is always pulled up.

MD18 & MD19 configuration are correct: pulled up with 470K.

In Atlas datasheet, strap option table , these straps are pulled up and tehre is a table for typical setting. I can't find where these straps are set to 0?

In addition, I suggest you to have a look in the reference schematics of Atals and verify the strap option setting. you can find also that MD18 & MD19 are pulled up.

Hope that helps.

jalonso1 · ‎2006-12-05

Posted on December 05, 2006 at 14:53

Hello,

Sorry for my English (I am from Spain), but I think I was misunderstood. Or perhaps I did not understand your answer.

We have followed all the recommendations from the datasheet and reference schematics, in order to configure STPC Atlas in DX1 mode, with HCLK and MCLKO pins configured as outputs. Thus, we have added 470k pullup resistors to MD14, MD18 and MD19, as I said, and a pulldown to MD40 also, apart form the rest of strap options as recommended.

We have tested succesfully that these signals are at correct levels when starting up. But when accessing STPC Atlas strap registers through addresses 0022h/0023h(pages 38-41 of the STPC Atlas datasheet)we read a 0 in bits corresponding to MD14, MD18 and MD19. Other bits are correct. We do not understand it, and would like to know if it could be related with the inestability problems we are facing with (unwanted resets and software exceptions).

Thanks again.

kaouther · ‎2007-03-06

Posted on March 06, 2007 at 10:56

Hello,

Did you solved the instability issue of your system?

Thanks.