Using FAIM for Hi-Z port pin while LPC844 held in reset

mike_hackett — Tue, 29 Jun 2021 10:33:22 GMT

Hi.

If the LPC844 processor is configured so that a port pin is configured using the FAIM for Hi-Z , (No pull-up, no pull-down). If the Reset pin is HELD low, while held low , does the pin state match that as for the FAIM config.

I have a situation, with are external volt-supervisor, due to possibility of slow ramp supply volts.

I don't want the port pin to source current from the weak pull-up, during Reset Low.

My code puts pin state o/p low as soon a it can. Using FAIM I can have hi-z pin state, but user manual seems to suggest it only kicks in AFTER Reset, not while Reset is active.

Testing seems to show that the pin is hi-z, but can you please confim.

Thanks

Re: Using FAIM for Hi-Z port pin while LPC844 held in reset

ZhangJennie — Thu, 01 Jul 2021 14:27:13 GMT

Hi Mike

FAIM is for MCU initial configuration AFTER reset. The initialization includes:
− FRO clock frequency
− Pin configuration with pull ups, pull downs, and tri state
− SWD
− ISP interface for programming and ISP pins

One reset cycle is needed to make this initialization take effect. And because FAIM programming voltage range is 3.0 V ≤ Vdd ≤ 3.6 V. So during ramup that Vdd is lower than 3.3v, FAIM setting can't take effect.

We don't have official data of pin status during RESET pin low.

Have a nice day,

Jun Zhang

LPC MicrocontrollersのトピックRe: Using FAIM for Hi-Z port pin while LPC844 held in reset

Using FAIM for Hi-Z port pin while LPC844 held in reset

Re: Using FAIM for Hi-Z port pin while LPC844 held in reset