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

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

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Contributor III

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 

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NXP TechSupport
NXP TechSupport

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

BR

XiangJun Rong

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NXP TechSupport
NXP TechSupport

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

BR

XiangJun Rong

pastedImage_1.png

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Contributor III

thank you

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