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P1011 POR configuration pull-ups query

Question asked by Andy Jones on Jul 5, 2017
Latest reply on Jul 6, 2017 by Andy Jones

I'm trying to build up a picture of what POR pins require external pull-ups/downs, as opposed to making use of internal pull-ups, on the P1011, but I'm struggling to get a consistent interpretation of data in two documents:


Document 1: Regarding Section 1.2, "Table 1. P1011 Pinout Listing" of

"P1011 QorIQ Integrated Processor Hardware Specifications, Document Number: P1011EC, Rev. 1, 03/2012", each Signal with a reference to Note 4 has the benefit of an internal Pull-Up applied during POR.  This does not apply to all signals associated with the POR configuration. Of the signals that do have this facility, some are normally I/O, others are normally Outputs.


Document 2: Regarding chapter 3, "Table 3-2. Reset configuration signals" of

"P1020 QorIQ Integrated Processor Reference Manual Supports: P1020 and P1011, Document Number: P1020RM, Rev. 6, 01/2013."


The table is introduced with the statement

"Most of the reset configuration signals have internal pull-up resistors so that if the signals are not driven, the default value is high (a one), as shown in the table. Some signals do not have pull-up resistors and must be driven high or low during the reset period."

and lists the functional signal names that are associated with reset configuration names, and the Default, which is expressed as:

"Must be driven": for all cfg_xxx_pllx inputs (some of which are normally Outputs or I/O without internal pull-ups, but others are I/O which Document 1 identifies as having Internal pull-ups, e.g. TSEC_1588_CLK_OUT, cfg_ddr_pll0 - and for which the group being 111 is a valid configuration), so how does the statement in italics above relate? Must it really be driven, or is it pulled up?


"All ones": for cfg_gpinput[0:15].  These do all have pull-ups, so this is consistent with Document 1.


"1" or strings of "1": Again, a problem as there are a number of examples that Document 1 suggests do not benefit from having pull-ups during POR,, e.g. I/O signal MSRCID0, cfg_elbc_ecc, or Output signal UART_SOUT0, cfg_eng_use[3].  Are these really all equipped with pull-ups or must they be driven?


Please tell me, what aspect have I overlooked?  Is the P1011 and P1020 data meant to be the same in respect of these POR configurations and pull-ups?



Andy Jones