Pullup resistors

Questions on other types of hardware and getting it talking to the ARM CPU
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Pullup resistors

Post by YahooArchive »

>from help line
>I am using IO(0) to IO(7) and IO(10) to IO(12) to drive 4 line character LCD
panel with ARMmite PRO. Do I need to have pull up resistors in all IO outputs?
Will 2.7K ohm resistor be alright if I need pull ups? Is it different for

There are no builtin pullup resistors on the LPC2103 (used in the ARMmite and
ARMmite PRO).

So if what you are interfacing to needs a pullup, you'll have to add it. I
usually use 10K, though 2.7K would be OK, just it consumes more power.

If you read an IO on an LPC2103 and that IO is floating, you will get who knows
what (and it may depend on the phase of the moon). In this case when what's
driving the IO may not be driving all the time, you may want to add a pullup.

Normally you would not add pullups to bi-directional data lines.

You might want pullups on CS or WE control lines, especially as immediately
following reset, all lines are configured as inputs until you program starts up
and re-configures them.

The newer Cortex parts have optional resistors on most IOs

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