Siemens SINUMERIK 802C base line Technical Manual page 57

PLC project
S7-200
ladder diagram
Overview of commands
SINUMERIK 802C base line
Start-Up
In any case, the PLC 802 Programming tool manages one project (logic
operations, symbols and comments). The download function is intended to
store all important information of a project in a control system.
The control system is able to store max. 4,000 instructions and 1,000 symbols.
The required PLC memory is influenced by the following components:
Number of instructions
z
Number and length of the symbol names
z
Number and length of the comments
z
A ladder diagram is a graphical programming language similar to electric circuit
diagrams.
When creating a program using the ladder diagram form, then you will work
with graphical components to create the networks of your logics. To create your
program, you can use the following elements:
Contacts constitute a switch through which the current can flow. Current,
z
however, will only flow through a normally open contact if the contact is
closed (logical value 1). Current will flow through a normally closed
contact or a negated contact (NOT) if the contact is open (logical value
0).
Coils constitute a relay or an output which is updated by the signal flow.
z
Boxes constitute a function (e.g. a timer, counter or arithmetic operation)
z
which is carried out at the moment when the signal flow reaches the box.
A network consists of the elements mentioned above, forming a closed circuit.
The current flows from the left conductor bar (in the ladder diagram symbolized
by a vertical line at the left window) through the closed contacts, enabling coils
or boxes.
Table 4–7 Operand identifers
Operand ID Description
V Data
T Timers
C Counters
I Map of digital inputs
Q Map of digital outputs Q0.0 to Q7.7
M Flags
SM Special flags
AC ACCU
Table 4–8 Generating the addresses for the V range (see user interface)
Type Code
(DB No.) (Channel/ Axis No.)
00
(00-79)
V0.0 to V79999999.7 (see Table 4-8)
T0 to T15
C0 to C31
I0.0 to I7.7
M0.0 to M127.7
SM0.0 to SM 0.6 (see Table 4-10)
AC0 ... AC3
Range No.
Subrange
00
(00-99) (0-9)
Range
Offset Addressing
0 000 symbolic
(000-999)
Start-Up
(8-digit)
4-19