STC is a Chinese maker of microcontroller chips, mostly 8051 architecture. The whole environment is characterised by a lack of English language information, or unreliable information.
The U8W is a programmer for some of their chips, and works in concert with their ISP programming software (Windows).
Above is the U8W. It was supplied without any documentation by an Aliexpress seller. Requests from the seller and from STC have not yielded any information.
Some functions are labelled in English sufficiently to make a good guess how it works, but others are not.
The ISP software client has links to manuals, but the links are dead… Chinese Quality.
There are two USB connectors, a type A jack (like found on computers), and a micro jack. The labels are the same, but it is clear that they have different functions.
Above is the label that appears on both USB jacks.
It seems that the micro jack is for power only, and only the type A jack has the USB data wires connected. It might be trying to say that the micro jack is for additional power if the computer USB connection cannot supply sufficient current.
The U8W draws 70mA when powered up and no device connected.
Above is the label on “Key 1 Download key”. It seems to be used to download an image previously stored on the U8W to the target in “offline” mode.
Above is the label on “Key 2 Update key”. It is not clear how it differs from Key 1.
Small switch on side
Above is the labeling for the small switch on the side. It perhaps relates to selection of ‘normal’ operation, or upgrade of the MCU internal to the U8W.
I will update this with knowledge gained.