Appendix
B
Display Systems
B-3
B.4
Data Transmission Structure
A basic understanding of RS-232 data transmission structure enables you to begin programming
automated controls for the Marquee
projector. Once you have become familiar with this structure,
refer to the two tables later in this document. These tables list the specific binary codes required for
all available commands and provide examples of commands most commonly used in typical
applications. Use these tables to quickly begin programming the controller without having to
determine each complete data stream yourself.
Every Marquee serial communication consists of two parts: the transport layer and the message. In
general, information in the transport layer determines how information is passed to and from the
projector and the message contains the specific information being passed. Both parts are shown in
Figure B-2 and are further described below.
Note:
Throughout this document a number preceded by a "$" is a hexadecimal value.
X
0
1 2
3 4
5
6
7
X X
St
ar
t M
es
sa
ge
M
es
sa
ge
L
en
gt
h
D
es
tin
at
io
n
(2
b
yt
es
)
S
ou
rc
e
Fi
el
d
(2
b
yt
es
)
C
om
m
an
d
C
od
e
(1
b
yt
e)
P
ar
am
et
er
#
1
(1
b
yt
e)
P
ar
am
et
er
#
2
(1
b
yt
e)
C
he
ck
su
m
(o
pt
io
na
l)
E
nd
o
f M
es
sa
ge
(01)
HEADER
BODY
(00)(0E)
MESSAGE BYTE
TRANSPORT
LAYER BYTE
(binary)
TRANSPORT
LAYER BYTES
(binary)
Figure B-2. A Complete RS-232 Data Transmission
B.5 Transport
Layer
Every message must include a transport layer in order to be recognized as a complete RS-232 data
transmission. As shown in Figure B-2, transport code appears at the beginning and end of every RS-
232 communication. A transport layer has three main functions
:
3. To mark the start and finish of each message.
4. To prevent data overflow.
5. To separate transport layer codes from message data.
Special control codes reserved only for the transport layer are shown in Table B-1.
Table B-1. Transport Layer Special Control Codes
Binary
(Hex) Value
Mnemonic
Description
Function
$01
SOH
start of header start of message
$0E
SO
shift out
end of message
$13
XOFF
transmit off
stop transmission
$11
XON
transmit on
resume transmission
$1B
ESC
escape
next byte has been shifted
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
