Siemens SIMATIC TIWAY 1 - Manual (Page 182)

USING THE NON-INTELLIGENT TERMINAL PROTOCOL
UNILINK HOST ADAPTER A-6
USER MANUAL
Figure A–2 illustrates how a TIWAY I Primitive is enclosed in the adapter
command string which is enclosed in the NITP message structure.
Length
Primitive
Code
Descriptor
Field(s)
Data Unit
Field(s)
Command Code
Secondary
Address
Network Data
TIWAY I Primitives
: Adapter Data Check Sum
UNILINK Host Adapter Commands
Message
Character
Count
;
NITP Protocol Message Frame
Figure A–2 Illustrative NITP Message Structure