Pull up or down ?

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FFMan
Posts: 502
Joined: 09 January 2010, 12:52 PM

Pull up or down ?

Post by FFMan »

I'm using serial channel 2 on a zx24n with a mask of bx00001000 connected to a max232.

So non-inverted right ? Should I have pull up or pull down resistors on pins 6 & 11 ? I've got 10k pull-ups but i'm not getting any output and want to eliminate this as a possible cause.

thanks
dkinzer
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Posts: 3120
Joined: 03 September 2005, 13:53 PM
Location: Portland, OR

Re: Pull up or down ?

Post by dkinzer »

FFMan wrote:Should I have pull up or pull down resistors on pins 6 & 11 ?
The way to remember whether to use a pullup or pulldown is to consider that you need to pull the line to the "idle" state. A non-inverted, TTL-level serial input or output idles at +V so you need a pull-up to achieve the idle state. Conversely, an inverted, TTL-level serial input or output idles at 0V so you would need a pull-down to achieve the idle state.
- Don Kinzer
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