You should not rely on the internal pull downs to set your boot mode. You should have external pull downs to set the boot mode that you want.

Jeff

jeff; thanks for the reply;

but the datasheet, and bootup manual for am18xx; says use Pu/Pd; needed only if the pins are routed out.

so; you say even if the pins have no connection; still I should go ahead and bring out ALL the 8 Boot0 to Boot8 pins out and place resistors on them?

If you think so then I will; I was just trying to eliminate an un necessary cost. 8 resistors that do no other good!

Please let me know; thanks.

I'm trying to find the sections you are referring to which says the Pu/Pd are not needed. Can you give me a page number or table number in each document?

Since you plan to use I2C0 EEPROM mode, you could just use 1 stronger down resistor and connect all the boot pins to that. Theres no need to put 8 in parallel.

Jeff

Take care. This would basically short all the 8 pins making them useless for use for i.e. GPIOs, LCD (bits 8-15) or UPP_XD (bits 0-7) afterwards...

I wouldn't recommend going down this path
  Søren

Jeff;

it is in different places/links but here are some:

1- Section 4.3, page 64:   4.3 Pullup/Pulldown Resistors

.....

"An external pullup/pulldown resistor needs to be used in the following situations:

• Boot and Configuration Pins: If the pin is both routed out and 3-stated (not driven), an external

pullup/pulldown resistor is strongly recommended, even if the IPU/IPD matches the desired value/state."

(( but in my case; I would NOT route it out or Use it)) So it applies to this case.

2- Appendix A of the Bootloader manual says the I2c0 EEprom is the boot type: 0000 0000 .

3-  In Am1808 Datasheet, Page 35 :

3.7.11 Boot

 In Here: Section: 2.2.5 of: 

OMAP-L13x / C674x / AM1x Schematic Review Checklist:

http://processors.wiki.ti.com/index.php/OMAP-L13x_/_C674x_/_AM1x_Schematic_Review_Checklist#Boot_modes

Boot modes

• CAUTION: Be careful if anything is hooked up to these pins (i.e. if the pins are have multiple uses such as GPIO or other peripherals). You must make sure that the boot pins are at the proper levels when power-on reset occurs such that the correct values are latched in order for the device to boot correctly!

 ----------------------------------------------------------------------------

For each cpu that would be 8 resistors plus Assembly costs; there should be a cheaper way to do it.

However I like your idea of tying all 8 to a single resistor. If that doesn't cause any problems; then I'll do it.

In otherwords; under the IC itself; I would tie all the 8 boot pins togeter and bring one line out and connect to a resistor;

Am I correct?

thanks for your help.

Hi,

Actually I think this would not short them to Zero volt or +Vcc; since they all connect through a single resistor to Ground.

the Datasheet says that they are all pulled down with Weak PullDown during Reset.

But you are correct that this will make them useless for other things.

thanks for the advise.

Just to clarify - I didn't expect any problem with the connection to GND/VCC - Only with shorting the pins together, which would effectively make the useless for other stuff :-)
  Søren

In the case that the pins are routed out, it is strongly recommended to use the external pulls because of the increased possibility of interference. However it is good practice to use them in any case, even though the possibility of issues is less.

Yes if you are not going to use any of those pins, then you can tie them all to ground via one resistor. However you lose lots of debug options by not using separate pull downs, since this forces you to always be in I2C0 EEPROM boot.

Jeff

Jeff, thanks for the clarifications.

The more I know of am18; the more i like it!

ma