Modicon Driver Addressing

The allowable range of addresses is dependent upon the device with which you are communicating. For example, a PLC may only have 500 holding registers, and thus it can only address either 40001 through 40501, OR 400001 through 400501 (whichever you prefer), even though the protocol allows for addresses much higher than this.

The table below identifies the value ranges for Modicon outputs, inputs, input registers, and holding registers.

 

I/O Type	Text Prefix	5 digit address	6 digit address
Holding Coil	HC1 - HC65536	00001 – 09999	000001 – 065535
Input Coil	IC1 - IC56636	10001 – 19999	100001 – 165535
Input Registers	IR1 - IR65536	30001 – 39999	300001 – 365535
Holding Registers	HR1 - HR65536	40001 – 49999	400001 – 465535
Data Logger	DL1:1 – DL16:8

Bit Addressing

An individual bit in a register (either an Input Register or a Holding Coil) may be read or written (for Holding Coils) by appending the address with "/x" where x has a value from 0 to 15 and indicates which bit is to be used.  For writes, a read\modify\write cycle is used on the register as the Modicon protocol does not have a bit operation function.

 

Float Addressing

If required, you can use floating point addressing with VTS. The process will require an adjustment to the way the address is provided in order to reach the correct register. 

Modicon registers are 16 bits wide.  In order to get a float address you will need to read 2 sequential registers to get 32 bits.  To do this, you will need to know the lowest register address of the pair.  Note that this may be odd or even and differs by device. 

The address will be formed by entering the lowest address of the pair with the suffix of /FLOAT. e.g. IR9/FLOAT will read the register pair at IR9 and 10, and return the combined value as a float. 

Note that driver options determine how the 4 bytes in the combined register pair are ordered to form the float as this will differ by device.

 

 

Modicon Driver Addressing: Modicon Driver Tag Properties

Modicon Driver Tag Properties Folder Tab	Property	Value
Options Tab	Comm Channel	Serial RTU
Serial Tab	PLC Address	1
Serial Tab	Time-Out Limit	0.5 (Make it shorter if Scan Interval is going to be very short)
Serial Tab	Port	COM2 (name of Serial Port tag)
Serial Tab	Retry Delay	0
Serial Tab	Hold	deselected
Serial Tab	Retries	2
Serial Tab	RTS Key Off Delay	0

Modicon Driver Addressing: Serial Port Tag Properties

Serial Port Tag Properties Folder Tab	Property	Value
Settings Tab	Port Number	2
Settings Tab	Data Bits	8
Settings Tab	Stop Bits	1
Settings Tab	Baud Rate	9600
Settings Tab	Parity	No Parity
Settings Tab	Echo	deselected
Settings Tab	RTS Keying	deselected
Settings Tab	Key Up Delay	0.1