Automation Direct D0-DCM, Руководство пользователя

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User Application
Guidelines
RLL
Programming
for Communications
4–3
RLL Programming for Communications
DL05/06 Data Communications Module, 1st Edition, 08/05
Network Instructions
The Read (RX) and Write (WX) instructions are used by the master PLC to Read a
block of data from another PLC or Write a block of data to another PLC. To perform
their functions, the RX and WX boxes must be preceded in the ladder logic program
by two Load instructions and one Load Address instruction.
The Load and Load Address instructions load communication parameters into the
accumulator and the first and second level of the accumulator stack. The RX or
WX instruction takes these parameters from the stack and the accumulator and
prepares the data to be sent over the network. If you need to know more about the
function of the accumulator and the accumulator stack, refer to the User Manual for
your PLC.
For network communications, you build
the Read (RX) or Write (WX) instructions
into a routine which requires the four
instructions you see to the right. The
function of each of these instructions is
explained below or on the next page. They
must be used in the sequence shown.
LDA
O aaa
LD
A aaa
LD
A aaa
RX or WX
A aaa
The first Load (LD) instruction accepts either a constant or a variable. Use a “K” to
designate the number as a constant. Use a “V” if you are entering the address of a
register. The contents of that register perform the same function as the constant
shown below. For example, you could use V2000 in place of K0114. If the contents of
V2000 is the number “114,” the function would be the same. Using a variable allows
changing parameters while the program is running. It is recommended, however, to
use a constant when possible.
LD
K114
1 1 4 0 K
Upper Byte
Lower Byte
Slave Master DCM
Slave Address # (Hex)
Slave Device on Network
DCM Slot Number
Master PLC
Read (RX) and
Write (WX)
Instructions
Building the
Read (RX) or
Write (WX)
Routine
The First LD
Instruction