DL205 User Manual, 4th Edition, Rev. B
5–207
Chapter 5: Standard RLL Instructions - Modbus
1
2
3
4
5
6
7
8
9
10
11
12
13
14
A
B
C
D
MRX Number of Elements
MRX Exception Response Buffer
MRX Example
DL260 port 2 has two Special Relay contacts associated with it (see Appendix D for comm
port special relays). One indicates “Port busy” (SP116), and the other indicates ”Port
Communication Error” (SP117). The “Port Busy” bit is on while the PLC communicates
with the slave. When the bit is off the program can initiate the next network request. The
“Port Communication Error” bit turns on when the PLC has detected an error. Use of this bit
is optional. When used, it should be ahead of any network instruction boxes since the error
bit is reset when an MRX or MWX instruction is executed.
Typically network communications will last longer than one CPU scan. The program must
wait for the communications to finish before starting the next transaction.
Number of Elements
Operand Data Type
DL260 Range
V-memory V
all (see page 3-56)
Constant K
Bits: 1-2000
Registers: 1-125
Exception Response Buffer
Operand Data Type
DL260 Range
V-memory V
all (see page 3-56)
This rung does a Modbus read from the first 32 coils of slave address number one.
It will place the value into 32 bits of the master starting at C0.
SP116
Port 2 Busy Bit
C100
Instruction Interlock Bit
MRX
CPU/DCM Slot:
CPU
Port Number:
Slave Address:
Function Code:
Start Slave Memory Address:
Start Master Memory Address:
Number of Elements:
Modbus Data Type:
Exception Response Buffer:
K2
K1
01 - Read Coil Status
K1
C0
K32
584/984 Mode
V400
RST
C100
Instruction Interlock Bit
1
