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Connection of RESn Pin — Parallax Forums

Connection of RESn Pin

aeae Posts: 7
edited 2009-10-28 15:28 in Propeller 1
Hi,

In my propeller project I·used pre programmed I2C eeprom so I don't need to pogram in runtime again.

So what is the better connection about the RESn pin;

· I- Leave unconnected.
·II-·Connect to VDD directly
III- Connect to VDD·via some resistor. (ie 5K, 10K )

or any other.

Thanks,

Comments

  • LeonLeon Posts: 7,620
    edited 2009-10-26 14:17
    You can leave it unconnected.

    Leon

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    Amateur radio callsign: G1HSM
  • jazzedjazzed Posts: 11,803
    edited 2009-10-26 16:41
    Leave it unconnected as long as BOEn is pulled to low to VSS/ground. If BOEn is pulled high, RESn will be asserted.
  • aeae Posts: 7
    edited 2009-10-27 07:23
    If the RESn pin leave unconnected, I think the propeller chip will get reset cause of Electromagnetic noise in the industry. The end product will be used in foctories.

    even I tested in the office chip gets reset when I am touching my oscilloscope prob to RESn pin.

    So I am not sure about it.

    III, looks like a better solution. To connect via 1K2 resistor to VDD.
  • Cluso99Cluso99 Posts: 18,069
    edited 2009-10-27 10:26
    It is normal to not connect anything to the -Res pin. However, if you expect a noisy environment, a 10K pullup will not hurt.

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    Links to other interesting threads:

    · Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
    · Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
    · Prop Tools under Development or Completed (Index)
    · Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
    · Search the Propeller forums·(uses advanced Google search)
    My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
  • MagIO2MagIO2 Posts: 2,243
    edited 2009-10-27 11:10
    Or make it a pulldown ... then the prop does not add any electromagnetic noise to the factory ;o)
  • Cluso99Cluso99 Posts: 18,069
    edited 2009-10-27 18:58
    MagIO2: Someone not in the know may take you seriously LOL (A pulldown will hold the prop in reset)

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Links to other interesting threads:

    · Home of the MultiBladeProps: TriBlade,·RamBlade,·SixBlade, website
    · Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
    · Prop Tools under Development or Completed (Index)
    · Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) ZiCog (Z80) , MoCog (6809)
    · Search the Propeller forums·(uses advanced Google search)
    My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-10-27 20:12
    I work in a very electromagnetically noisy environment. I do have to program at run-time, so I have (after much testing) ended up with a 2.2K pull up on the RESn (with the internal 5K, with BOEn low, equates to about 1.53K -- or 2.2mA -- seem plenty low enough current for the transistor on the prop plug). But even with that I would get random resets, so I have also put a 0.1µF capacitor on it as a low-pass filter. Now I don't get resets and I have never had any programming or other issues. This is an extreme setting. The prop resides only inches away from high voltage, very noisy transformers.
    I wish I could have the option of connecting RESn directly to the 3.3V, but I don't. That would be the route I would take.

    Here is another question: what is the benefit of having BOEn high? This pin (when low) will shut off the prop when the voltage is too low. But the prop likely functions at lower voltage than the brownout limit it set to. I under stand the basics as to what brownout enabled/disabled mean, but what are the benefits to either setting? Brownout disabled seems to be a rare design choice.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!

    Some of my objects:
    MCP3X08/4 ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
    String Manipulation Library - Don't make strings the bane of the Propeller, bend them to your will!
  • DroneDrone Posts: 433
    edited 2009-10-28 10:53
    Bob Fwedd,

    So there is an internal 5k pull-up on RESn? Where did you find this specification?

    Prop data sheet says maximum 500uA on forward biased protection diode.

    Chip Gracey in his propeller programming propeller object here obex.parallax.com/objects/61/ recommends a 1 meg pull-up on RESn. Hmmm...

    Rgds, David
  • LeonLeon Posts: 7,620
    edited 2009-10-28 13:50
    That's for two Propellers with one driving the others RESn pin, it isn't relevant to a single Propeller.

    Leon

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    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 10/28/2009 1:59:47 PM GMT
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2009-10-28 15:28
    Drone said...
    So there is an internal 5k pull-up on RESn? Where did you find this specification?
    Datasheet v1.2 said...

    BOEn - Brown Out Enable (active low). Must be connected to either VDD or VSS. If low, RESn becomes a weak output (delivering VDD through 5 k&#937[noparse];)[/noparse] for monitoring purposes but can still be driven low to cause reset. If high, RESn is CMOS input with Schmitt Trigger.

    Drone said...
    Prop data sheet says maximum 500uA on forward biased protection diode.
    This is for the diodes: Vss >| Pin >| Vdd (">|" are diodes -- squint a little). They really only apply when the input voltage is 0.3V above Vdd or 0.3V below Vss. So if you are pulling up to Vdd, you don't need to mess with the 500µA on forward biased protection diodes.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    April, 2008: when I discovered the answers to all my micro-computational-botherations!

    Some of my objects:
    MCP3X08/4 ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
    String Manipulation Library - Don't make strings the bane of the Propeller, bend them to your will!
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