Why is DM8127/DM8148 always in RESET, i.e., RSTOUTn_WD_OUTn is always asserted (always 0)

Nan Li2

Prodigy 160 points

Hi, all

The hardware is designed by myself, but the powering parts are copied from taht of APPRO-IPNC.

And i haved measured the output TPS659113, the results are qualified in both timing and rating

And, i verified the following conditions:

1、The powering up sequence is correct, i have measured the sequence pairwise~~

2、The voltage ratings are correct (1.2V 1.5V 1.8V 3.3V are all present)~~~

3、The crystal are working in a correct way (i have measured the waves, both are correct (20MHz & 22.5792MHz))

Nevertheless, i found that, RSTOUTn_WD_OUTn is always 0 (Logic Low) while POR is already deasserted from the state " POR = '0' ".

can anyone explain why should this happen

over 9 years ago

0 Pavel Botev over 9 years ago

TI__Guru**** 170625 points

Hi Nan,

For RSTOUT_WD_OUTn is asserted (go low) when PORn is active only when BTMODE[11] is 0. As you have RSTOUT_WD_OUT is asserted and never goes high after is asserted, then I assume your BTMODE[11] is 0.

Do you install proper external pull down resistor on the RSTOUT_WD_OUTn pin? On DM814x EVM we have 2.2K external pull down resistor.

RSTOUT_WD_OUTn signal is de-asserted (high) when the device is out of reset, so check all reset signals are not active, not only PORn, but WDT reset, RESETn, etc

RSTOUT_WD_OUTn pin remains asserted until PRCM release the host Cortex-A8 from reset. Check if Cortex-A8 is released from reset.

BR
Pavel