JIM LAMBERSON

Confused about internal pull-ups/pull-downs on 5223x family

Discussion created by JIM LAMBERSON on Jan 10, 2008
Latest reply on Jan 11, 2008 by James Williams
I've read the MCF52235 ColdFire Integrated Microcontroller Reference Manual from cover to cover and I'm still a bit foggy about the meaning of the "pull-up/pull-down" column in Table 2-1.
 
The column heading cites Note 2, which says "all signals have a pull-up in gpio mode." I assume this to mean that the device unconditionally activates an internal pull-up for any multi-function pin that is operating as a gpio, but the internal pull-up is not activated for other modes unless there is an entry in the column that indicates otherwise. Is this correct?
 
All pins that have a gpio function are configured to operate in gpio mode upon reset, and thus all of these pins are pulled up by the internal pull-ups by default. Are the pull-ups active when reset is asserted, or only upon release of reset?
 
Some pins (e.g., IRQ2) indicate "pull-up" in the column and cite Note 6, which says "for primary and gpio functions only." I assume this to mean that the device activates an internal pull-up, but only when the pin is operating as either gpio or primary function, and in all other cases the pin has no internal pull-up. Correct?
 
The RSTI pin indicates "pull-up" and cites Note 9, which says "RSTI has an internal pull-up resistor, ..." Based on this, I assume that the TEST and JTAG_EN pins, which indicate "pull-down," have internal pull-downs, and thus it is not necessary to tie them to ground or supply external pull-downs. Correct?
 
Similarly, RCON indicates "pull-up," which is assumed to mean that it has an internal pull-up, and thus this pin may be left disconnected to permanently disable the ezport. Correct?
 

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