Siemens SIMATIC TIWAY 1 - Manual (Page 169)

ERROR CODES AND DIAGNOSTICS
UNILINK HOST ADAPTER 6–6
USER MANUAL
6.2 PRIMITIVE ERRORS
The HIU function will respond to the 02, 03, and 04 TIWAY I Primitives, just like
Network Interface Modules (NIMs). The following Primitive response errors
will be returned to any device sending an invalid Primitive. The responses to
valid Primitives are defined in Paragraph 2.7.
CODE MEANING
00 The Primitive is currently not implemented.
03 The Primitive is too long.
04 The Primitive is too short. A Primitive must include a Length word and
a Primitive code so that the smallest Primitive length is three bytes.
05 The message length and the Primitive length are not equal.