Вот про это я и говорил:
03 ILLEGAL DATA VALUE
A value contained in the query data field is not an allowable
value for server (or slave). This indicates a fault in the
structure of the remainder of a complex request, such as that
the implied length is incorrect.
It specifically does NOT mean
that a data item submitted for storage in a register has a value
outside the expectation of the application program, since the
MODBUS protocol is unaware of the significance of any
particular value of any particular register.
05 ACKNOWLEDGE
я так понимаю устроййстро занято не просто чем-то, а программированием. (Specialized use in conjunction with programming commands.)
Интересно, в стандарте (MODBUS Application Protocol Specification V1.1) упоминаются межсетевые шлюзы (GATEWAY), но нет никаких подробностей
