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ADuC7060/61: NTRST pin external pull-up

Question asked by V.M. on Aug 3, 2011
Latest reply on Sep 15, 2011 by MikeL

In specs Rev. C, page 17 (pin 45) and page 19 (pin 29) it says :

The ADuC7060 enters serial download mode if BM is low at reset and executes code if BM is pulled high at reset through a 13 kΩ resistor.

The ADuC7061 enters serial download mode if BM is low at reset and executes code if BM is pulled high at reset through a 13 kΩ resistor.


In other words -- it is suggested that the external pull-up for the NTRST pin should be 13k.

 

On electrical pages of the same spec, page 8

 

Input Leakage Current     NTRST only: input (low) = 0 V                              ±1     ±10     μA
Input Pull-Down Current     NTRST only: input (high) = DVDD              30     55     100     μA

LOGIC INPUTS     All logic inputs
Input Low Voltage (VINL)                                                                                   0.4     V
Input High Voltage (VINH)                                                                 2.0                      V

 

With 100 μA (max) pull-down current and minimum of 2.0 V required at the NTRST input at Reset (when GP0PAR Bit 7 = 0, pull-down NOT disabled), and the supply voltage of 2.5 V ==== there is a maximum of 0.5 V that can be dropped across the external pull-up.

 

In other words --- I believe ---  the pull-up resistor attached to NTRST should be 5k or less.

Is this correct?

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