LPC MicrocontrollersのトピックRe: LPC54S018M: SWD's SWDIO and SWCLK pins pullup/pulldown

LPC54S018M: SWD's SWDIO and SWCLK pins pullup/pulldown

belmontbob59 — Wed, 18 Mar 2020 23:39:31 GMT

KEIL recommends to add pull up on SWDIO and pull down on SWCLK unless the device already include them internally. see below. Should I add them or not to my board with LPC54S018M?

ULINK2 User's Guide: Target Connectors

Re: LPC54S018M: SWD's SWDIO and SWCLK pins pullup/pulldown

xiangjun_rong — Fri, 20 Mar 2020 06:30:46 GMT

Hi, Bob,

Both of the SWDIO and SWDCLK signals have on-chip pull-up resistors as the following Fig from UM11155.pdf, so I think it is okay not to use any any external resistors.

But I have checked the schematics of LPC540xx, the SWDIO pin is connected with a 100K ohm resistor, so I think you can connect a 100K ohm resistor or not for the SWDIO pin, for the SWDCLK, it is unnecessary to connect any resistor.

Hope it can help you

XiangJun Rong

Re: LPC54S018M: SWD's SWDIO and SWCLK pins pullup/pulldown

belmontbob59 — Fri, 20 Mar 2020 16:07:15 GMT

thank you