Siemens SIMATIC TIWAY 1 - Manual (Page 177)

UNILINK HOST ADAPTER A–1
USER MANUAL
APPENDIX A
USING THE NON-INTELLIGENT
TERMINAL PROTOCOL
A.1 CHARACTERISTICS OF THE NON–INTELLIGENT TERMINAL
PROTOCOL
The Non-Intelligent Terminal Protocol (NITP) is a simple, character-oriented
method of data link communications using standard 7-bit ASCII codes. Both
command and response messages consist of starting and ending delimiters, a
character count or message length field, the body of the message, and an
error-checking code field as illustrated in Figure A–1.
: Character
Count
Message
Body
ECC
;
Figure A–1 NITP Message Structure
A.1.1 NITP Character Set
NITP uses the subset of standard ASCII codes, shown in Table A–1, to
communicate with a wide variety of host devices, from ASCII terminals to more
intelligent machines.