ivelegacy wrote:it seems we can't reprogram DS1981U chips, they are read-only
Of course. That's the whole point of these chips. Some of them also have programmable memory, but there will always be some form of read-only memory used for device identification purposes.
ivelegacy wrote:I do not know the "1wire-standard"
This is basically I2C bit-banging, but over a single wire used to alternatively convey the clock and data signals. Adapting an existing I2C design to 1wire is almost straightforward, except for the device power supply (true 1wire devices have only, well, one wire, and must use some form of vampire capacity to feed off the signals it receives on the wire in order to keep state and be able to do the bit-banging correctly).