Siemens SIMATIC TD 200 User Manual

D-2
SIMATIC TD 200 Operator Interface
C79000-G7076-C272-01
D.1 TD 200 Parameter Block
Understanding How Messages Are Displayed
The messages that the TD 200 displays are stored in the CPU. These messages
contain ASCII text, embedded values, and format information. The CPU enables
the messages through the use of a table of message-enable bits. There must be
one message bit allocated in V memory for each configured message. When the
program in the CPU says to display a message, the program sets that particular
message-enable bit. The TD 200 continuously polls the message-enable bits, and
if one of the bits is set, the TD 200 reads the corresponding message from the
CPU and writes the message to the display.
Understanding How the TD 200 Uses the Parameter Block
A TD 200 parameter block contains the TD 200 configuration information, and
must be created in the data memory (V memory) area of the S7-200 CPU in order
to establish an interface between the CPU and the TD 200. The TD 200 monitors
the CPU for either a parameter block identifier (ASCII characters “TD”) or an offset
to the parameter block.
If the TD 200 does not find the parameter block identifier (“TD”) in VW0, it uses the
value stored in VW0 as an offset to the TD 200 parameter block (see example in
Section 2.1). When the parameter block identifier is found, the next 8, 10, or 12
bytes provide the TD 200 with configuration information.
You can change the V memory address for the parameter block by means of a
setup menu. (See Section 3.8.) This allows you to connect two TD 200 units to one
CPU, with each TD 200 displaying different messages. Figure D-1 shows two
TD 200s connected to a single CPU. The parameter blocks for each of the TD 200
are stored in different V memory locations.
SIEMENS
TD 200
SIEMENS
TD 200
TD 200 Unit 1
Parameter block at VW0
V Memory
TD 200 Unit 2
Parameter block at VW40
VW0 Parameter block
for unit 1
VW40 Parameter block
for unit 2
Figure D-1 Displaying Different Messages on Two TD 200 Units
TD 200 Parameters and Messa
g
es

Siemens SIMATIC TD 200 Specifications

General

Brand	Siemens
Model	SIMATIC TD 200
Category	Recording Equipment
Language	English