Rockwell Automation 2711E PanelBuilder 1400e Modbus Communications - Manual (Page 43)

6–6 Defining Tags
Publication 2711E-6.12 – August 1997
5. To fill in the fields for data source, see
Specifying a Data
Source” later in this chapter.
Modbus Address Space
Modbus devices can contain four distinct address spaces. Two spaces
are reserved for Coil data and two are reserved for Register data. The
PanelView terminal can only write to one of the two Coil address
spaces but can read from both spaces. The same is true for the two
Register address spaces.
Modicon controllers store read and write address spaces in the
following data table locations:
Reference Address Type Data Access Description
0 Discrete
Output or Coil
(internal) bit read or
write Use to drive a real output through an
output module or to set one or more
internal coils. A coil can be used to
drive multiple contacts.
1 Discrete Input bit read-only Use to drive contacts in the logic
program. The input state is controlled
by an input module.
3 Input Register word
read-only Holds numeric inputs from an external
source (for example, a thumb wheel
entry, an analog signal or data from a
high speed counter). A 3x register can
also store 16 contiguous discrete
signals that are entered into the
register in either binary or binary coded
decimal (BCD) formats.