This article on 8051 based NuvoTon w78E052D says:
The nuvoTon w78E052D controller comes with UART boot-loader and can be directly programmed from the serial port.
The block diagram on NuvoTon website shows this to be the case. The datasheet for the device shows a 2KB LDROM which will be used to boot based on config bits. So this part must be protected from being overwritten I guess but in the same data sheet on section 8 MEMORY ORGANIZATION (page 14) there Memory Map shows a 16k ROM shown with no LDROM as an option. Wouldn't that make the UART stop working? Is there anyway to program it without the bootloader?
My understanding, atleast in the case of AVR series is, you would need a Arduino like bootloader to use FTDI like devices to flash the ROM through USB->serial. Without the bootloader, SPI with a programmer like VUSBTiny or USBAsp will be required. Is this correct?