Limp home mode

[Bob Wooten]

Ludis,

 

I was sooooooooo not clear, about what i meant.  what i meant is that 
I thought that the U17 chip was some kind of a watch dog   that I 
assumed that one of the RC networks to the left of the print were the RC 
networks that bring up the chip   that i could tie into the input to the 
chip   have the chip control the output.  I saw the Resister on the 
~ RESET line but thought that it was just a pull up for the line for some 
reason.  From the way that this chip is behaving it appears that this is 
some kind of power control chip (kind of like a on off relay).  I am also 
guessing that one of the RC networks on the left side (.2, .3, .5, .6, .7, .9, 
.10) control the timing of the chip coming up.  for example one of the RC 
networks brings VCC1 up.  another brings VCC2 up   
another brings up VCC3.  during this time it holds the ~RESET line 
  after all the power comes up it lets go of the ~RESET line.  

 

the question in my mind was which RC network controlled the ~RESET line 
  that is what i guessed was .2.  maybe i am reading in too 
much here but if this is not kind of how this chip works then what are all 
the RC networks for? (more rhetorical than anything i suppose).  


 

I guess i ought to just tie to the ~RESET line   get on with 
life????????

 

tanks again, sorry for the confusion.  

BW  

 

 

 


----- Original Message ----- 

From: Ludis Langens  

To: gmecm at diy-efi.org 

Sent: 3/11/01 11:53:02 PM 

Subject: Re: Limp home mode





Bob Wooten wrote:

  

  what I am

  ultimately trying to do is to pull the ~RESET line so that I can shut 
down

  the CPU.  with the emulator that I just bought.  I 
figured that I could tie

  into Pin 2 but it appears that this is not working as I guessed it 
would  by

  holding it down it appears that the entire CPU is still "dead"   
the

  emulator does not like that.

 

Pin _two_?  There's no chip in a '7730 where pin 2 is 
~RESET.  The

regular reset comes from pin 1 of U17.  You may notice a 5.1K 
pull up to

VCC.  I'm quite sure that everything driving the reset line has 
an open

collector driver.  That means that at most, you have to sink 
about 1ma.

 

-- 

Ludis 
Langens                               
ludis (at) cruzers (dot) com

Mac, Fiero,   engine controller goodies:  http://www.cruzers.com/~ludis/ 

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--- Bob Wooten

--- r71chevy at earthlink.net 

--- www.r71camaro.homestead.com 

 
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