AVR-Chat

Thanks Steven.  This will save me some hardware hassle.

Thanks/Jeff


From: STEVEN HOLDER 
Sent: Friday, October 16, 2009 2:47 AM
To: AVR-Chat@yahoogroups.com 
Subject: Re: [AVR-Chat] RESET connection between AVR and MCP23S17 port expander required?


  I don't think the reset line needs to be connected to the avr, but it does need to be connected, as long as the standard R/C reset line combination is employed (as you would do on the reset line of the avr) then it won't be a problem as long as the pulse width timing is maitained, from the data sheet the min pulse width is 1us, so your R/C combination needs to account for this, you could probably tie the reset lin of the avr to the reset line of the mcp, assuming the requirments above are met.
 
Regards

--- On Fri, 16/10/09, Jeff Blaine AC0C <keepwalking188@yahoo.com> wrote:

From: Jeff Blaine AC0C <keepwalking188@yahoo.com>
Subject: [AVR-Chat] RESET connection between AVR and MCP23S17 port expander required?
To: AVR-Chat@yahoogroups.com
Date: Friday, 16 October, 2009, 4:48 AM

  

In the normal configuration, the MCP23S17 needs 5 lines tied to the AVR. One of these lines is the RESET line input to the MCP chip.

As I read the data sheet, the use of that line is to allow the AVR to instruct that chip to perform a reset.

I do not anticipate needing to issue the instruction to reset the MCP via the AVR. The MCP will serve a similar function to a BCD in, one of 16 decoder. 

Question: In this case, where no master reset of the MCP is anticipated, would the RESET line still be required?

In one of my applications, I only have 4 lines available and the MCP would be the perfect solution. Assuming I won't need to use the RESET connection over to an IO on the AVR, that is.

Appreciate any comment from the distinguished group.

Thanks/jeff 

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