Don't Understand Power sequencing of TMS320F28035

Trung Ngo Minh said:

Question 1:  Now, using TMS320F28035 for control digital power and servo motor. I want to avoid short ciruit  of high-side and low-side MOSFET in Power on sequencing.  i've already used oscilloscope for measure waveform at Power on. There are a case  high-side and low-side MOSFET is ON simultaneously cause short-circuit.

GPIOs-state from power on to finish reset stage,  All GPIOs as input, but state its is denpend on internal PU/PD. so , before reset, How GPIOs is pull-up/pull-down?

You have found the information already based on your question below.  In the TMS320x2803x Piccolo System Control and Interrupt Reference Guide, page 97 provides you the information on what the default settings are for the GPAPUD and GPBPUD (pull up disable registers).

Trung Ngo Minh said:

 Question 2:  in SPRUGL8B (page 97), GPIO0-GPIO11 is disable and GPIO12-GPIO44 is enable the internal pullup (After reset).  as fig1, can use internal pullup for GPIO34, GPIO37 so that select Boot Mode?

Yes, if you use the internal pullup resistors for GPIO34 and GPIO37, you can boot up in the GetMode boot mode, which defaults to boot from flash.

If you are using these GPIO pins for other purposes on your board, ie. have them routed to other circuitry, I would suggest adding external resistors to augment the internal ones.  Generally speaking, the internal pullup resistors are not incredibly strong and may still be susceptable to noise in the system if these signals are routed to other portions of your design.

Review the section of text on page 96 of the same document.  I have copied below for your reference.  The area in bold is appropriate for when XRS is held low (in reset).

The pullup disable (GPxPUD) registers allow you to specify which pins should have an internal pullup resister enabled. The internal pullups on the pins that can be configured as ePWM outputs (GPIO0-GPIO11) are all disabled asynchronously when the external reset signal (XRS) is low. The internal pullups on all other pins are enabled on reset. When coming out of reset, the pullups remain in their default state until you enable or disable them selectively in software by writing to this register. The pullup configuration applies both to pins configured as I/O and those configured as peripheral functions.