A ''read-only'' [JSup tag|tag] cannot be changed by the [JSup application|application]: no [JSup Animations|animation] or [JSup Code script container|script] can change its value.
It can only be changed by an [IOHook|I/O hook] that reads the value of a remote device item.

A ''read-only'' [JSup tag|tag] without any [IOHook|I/O hook] defined is a '''constant''' tag. 
Use the [JSup tag initial value|initial value] to define the value of a constant tag.