Is factory burned bootloader required to communicate with ROM for NuvoTon w78E052D (8051)

Question

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?

Answer 1

I finally found the answer from the Nuvoton forum here which provides a general guide to programming Nuvoton micros. Could help someone looking for this info.

As per the guide:

Before using the ISP programming tool, user needs to program the boot code into LDROM by using a universal programmer or Nuvoton’s NuMicro® ICP Programming Tool, and the CBS(CONFIG0[7]) configured as boot from LDROM.

The device in question has a UART interface which can be used for programming. Unlike most devices I've encountered Nuvoton devices have the ROM divided into multiple logical areas:

1. Program the boot code into LDROM by using a universal programmer or Nuvoton’s NuMicro® ICP Programming Tool, and the CBS(CONFIG0[7]) configured as boot from LDROM.
2. Using the ISP programming tool to update APROM or CONFIG

The config bits which determine whether booting on reset is from LDROM or APROM is CBS (CONFIG.2)

The LDROM (Loader ROM) is where the bootloader goes into and the APROM (most probably stands for Application ROM) is where the the program goes into. Some info on the ISP process is also available in the datasheet but was not so clear to me. The ISP guide explain the process is much more clearly.