Automationdirect.com HX-ECOM Series - Read (WX) Instruction; Write (WX) Instruction

Ethernet Communications Modules, 3rd Edition, Rev. D
4–5
Chapter 4: RLL Programming for Communications
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Read (WX) Instruction
The Read (RX) instruction specifies the memory location to
be read from the responding PLC.
A block of data is read that begins at the specified memory
location and extends the number of bytes specified in the
second LD instruction.
In this example, the 8-byte block of data beginning at C100
and ending at C177 in the responding, or slave, PLC is read
(copied) into the initiating PLC’s memory beginning at
V40600.
Write (WX) Instruction
The Write (WX) instruction specifies the memory location to
be written to in the responding PLC.
A block of data is written that begins at the specified memory
location and extends the number of bytes specified in the
second LD instruction.
In the example, the 8-byte block of data beginning at V40600
and ending at V40603 in the initiating, or master, PLC is
written (copied) into the memory of the responding PLC,
beginning at C100 and ending at C177.
V40600
V40601
V40602
V40603
V40577
V40604
Initiating PLC
V4060
4
V4060
5
V4060
6
V4060
7
V4060
3
V4061
0
Responding PLC
R
e
ad
byte
byte
word 4words =8bytes
C100C177
bit
bit
V40600
V40601
V40602
V40603
V40577
V40604
Initiating PLC
V40604
V40605
V40606
V40607
V40603
V40610
Responding PLC
W
r
i
t
e
byte
byte
word
4words =8bytes
C100C177
bit
bit
V40600
V40601
V40602
V40603
V40577
V40604
Initiating PLC
V40604
V40605
V40606
V40607
V40603
V40610
Responding PLC
R
e
ad
byte
byte
word 4words =8bytes
C100C177
bit
bit
V40600
V40601
V40602
V40603
V40577
V40604
Initiating PLC
V40604
V40605
V40606
V40607
V40603
V40610
Responding PLC
W
r
i
t
e
byte
byte
word
4words =8bytes
C100C177
bit
bit
LD
K114
LD
K8
LDA
O40600
RX
C100
LD
K114
LD
K8
LDA
O40600
WX
C100