Section 8. Operation
481
8.10.3.5 Modbus Security
Q: What security options does the CR3000 offer for Modbus?
A: The Modbus protocol itself does not include security features, so the CR3000
does not offer security on ModbusMaster() or ModbusSlave(). Following are
security issues that come up:
•
MAC and IP filtering
•
Function code filtering
•
Privilege mapping rules by client (by port, IP, etc)
•
VPN tunneling
There are some third party Modbus security devices available that can be placed
between the CR3000 and the rest of the Modbus network. For example, see
tofinosecurity.com/products.
Q: Can I make some registers read-only and other registers writable?
A: Yes. By default all registers mapped to ModbusSlave() are writable. You may
make individual registers read-only with the ReadOnly() instruction in the
CR3000 CRBasic program.
The following example demonstrates how to report data by Modbus but not allow
a Modbus client to change register or coil values in the Modbus host:
•
Var can be viewed and changed
•
Reg() and Coil() can only be viewed
•
The CRBasic program can read from and write to all variables
Public
Var
Public
Reg(4), Coil(4) as Boolean
ReadOnly
Reg, Coil
BeginProg
'setup modbus tcp/ip slave
'readonly instruction above makes reg and coil read only / not
writable
ModbusSlave
(502,0,1,Reg,Coil,2)
Scan
(5,Sec,0,0)
var = var + 1 ' increment var
MBReg() = MBReg() + 0.1
'increment all the registers
MBCoil() = (NOT MBCoil())
'toggle all the coils
NextScan
EndProg
Summary of Contents for CR3000 Micrologger
Page 2: ......
Page 3: ......
Page 4: ......
Page 6: ......
Page 30: ......
Page 34: ......
Page 36: ......
Page 96: ......
Page 485: ...Section 8 Operation 485 8 11 2 Data Display FIGURE 110 Keyboard and Display Displaying Data ...
Page 487: ...Section 8 Operation 487 FIGURE 112 CR1000KD Real Time Custom ...
Page 491: ...Section 8 Operation 491 FIGURE 116 Keyboard and Display File Edit ...
Page 496: ......
Page 502: ......
Page 564: ...Section 11 Glossary 564 FIGURE 126 Relationships of Accuracy Precision and Resolution ...
Page 566: ......
Page 594: ......
Page 598: ......
Page 600: ......
Page 602: ......
Page 624: ......
Page 642: ......
Page 643: ......