LS1043A, Reset Configuration Pin Driving method

[logeshs]

Hi,

In LS1043A, For RCW source select we are using nor 16- flash, hence cfg_rcw_src value is 0_0010_0101. This bits corresponds to IFC_AD[8:15], IFC_CLE. The Pin description of these pins is given as below,

"This pin is a reset configuration pin. It has a weak (~20 kΩ) internal pull-up P-FET that
is enabled only when the processor is in its reset state. This pull-up is designed such that
it can be overpowered by an external 4.7 kΩ resistor. However, if the signal is intended to
be high after reset, and if there is any device on the net that might pull down the value of
the net at reset, a pull-up or active driver is needed."

We are selecting Boot Configuration pins through a pull up or pull down resistors. Say suppose as per above setting of IFC_AD[8:15], IFC_CLE lines as 0_0010_0101 we connected IFC_AD8, IFC_AD9, IFC_AD10, IFC_AD12, IFC_AD13, IFC_AD15 to a pulled down resistor(4.7Kohms) for selecting 16-Bit NOR Flash. 

As per pin recommendation do we need to have active driver for normal operation of IFC BUS or it can handle by itself?

[r8070z]

Have a great day,

I do not see if there is anything else connected to the IFC bus besides the nor flash. If there is only nor flash then IFC_CLE pin is open and IFC_AD[8:15] are not intended to be high or low after reset while they are not driven by the LS1043 or nor flash. Hence FC_CLE does not need for active driver. For IFC_AD[8:15] check that input leakage current of the LS1043 and nor flash data lines (J_lk) is low enough. I.e. J_lk*20k does not make the input voltage less then high level voltage. In this case internal pull-ups and 4.7k pull-downs should be enough.

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