Thank for you answer!
My question wasn't about the ability to writing or erasing ROM LPC540xx (everything is clear here). My question was about the physical implementation of ROM-cells in LPC540xx. Boot-ROM in microcontrollers can be implemented either as a mask-ROM, or as flash-memory with disabled write/erase (or in some other way).
I also know that microcontroller's manufacturers often implement boot-ROM based on flash-memory (physically = flash-cells), but with write-protected firmware. This flash-memory is programmed with firmware into the microcontroller during manufacturing.
What is mask-ROM I mean:
Mask ROM is a type of non-volatile read-only memory where data is physically hardcoded into the microchip during the semiconductor manufacturing process. Instead of being written electronically, the data (1s and 0s) is defined by the presence or absence of microscopic transistors or connections on the chip's photomasks.
Which of these boot-ROM types (ROM-cells) is used in microcontrollers LPC540xx?
Is there any documentation (or application note) about the boot-ROM-memory type in LPC540xx?
The "MCX series MCUs" you recommended aren't suitable for our project according to the requirements specifications, as they contain flash memory.
Besides these MCUs, we're also considering the i.MX RT1020 or LPC4370. What type of memory do they have? The LPC4370 and i.MX RT1020 are somewhat overkill for our needs. LPC540xx are preferable for us.
What do you mean "legacy"? They're not marked as "NRND" on the NXP website.