LPC55, what pins are active high/low by default in ISP boot mode

[dav1]

When ISP0 (PIO0_5 pin) is pulled low during cold-boot, the LPC55 enters ISP bootloader

couldn't really find the info in the datasheet or UM11126 pdf

I'd like to know if any of these pins are anything else thatn Hi-Z,
i.e. driven high or low or pu/pd..

[jay_heng]

For SPI, The SSEL, SCK, MOSI pin will be configured as SPI function, digital mode enabled, pull-up enabled, faster Slew rate for detection. and keep MISO pin to default state.

Once detection is done, all pins will be configured as SPI function, digital mode enabled, faster Slew rate

[jay_heng]

For I2C, all pins will be configured as I2C function, digital mode enabled, Filter disabled.

[dav1]

hi,

Does this mean that the default behavior with factory fuses and empty flash will enable all peripherals in the automatic probe feature?

ie uart gpio high, spi? 

would be great if the datasheet could list ALL gpio's reset and states during boot to avoid the risk of misatakes using say a gpio to enable something that ahould be off default that happens to be pulled up or driven high/low due to the boot loader

[jay_heng]

Yes,

it is not simple I/O level transition during automatic probe, it will check ping packet (0x5A, 0xA6)

[jay_heng]

For UART, The RXD pin will be configured as GPIO, digital mode enabled, pull-up enabled for auto baud function, and keep TXD pin to default state.

When Auto baud is done, then both RXD and TXD pin will be configured to UART function, digital mode enabled, faster Slew rate.

[EdwinHz]

Hi @dav1,

You are correct, there doesn’t seem to be any specific documentation about the state of these pins after the MCU enters ISP mode.

However, my guess is that you can base your answer for the state of each of these serial communication pins, by looking into the initialization that our SDK examples use. This should give you a good idea of the initialization state that the pins go through on ISP mode as well.

I hope this helps,

Edwin.