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Internals
Discrete Internals (Discrete)
Discrete Internals are denoted using “S” pre-fix (e.g. S1, S4, etc.). There are 1024 Discrete Internals available in
the EZ3-TouchPLC Modular. Internals are Read-write type and are used as “Scratch bits”. Discrete internal bits
are mainly used to control the user logic program. They do not represent a real physical device, like a switch,
output coil, etc. They are only internal to the CPU. You cannot program discrete internals as discrete inputs or
discrete outputs for the physical inputs or outputs.
Note: In this example, memory location S1 will be powered when input I1 turns on; you can then use a
discrete internal as an input in another rung.
Register Internals (Word)
Internal Registers are denoted using an “R” pre-fix (e.g. R1, R4, etc.). These are 16- bit Word data types
(registers). There are 8192 Internal Registers available in the EZ3-TouchPLC Modular. "R" are Read-
Write type of data registers.
System
System Discretes (Discrete)
System Discretes are denoted using an “SD” prefix (e.g. SD1, SD4, etc.). SDs are discrete memory locations with
pre-assigned functionality. There are many different types of System Discretes. They are used to help in logic
program development, provide system operating status info and more.
Note: Many System Discretes are preassigned a function.
System Registers (Word)
System Registers are denoted using an “SR” prefix (e.g. SR1, SR4, etc.). These are 16- bit Word data types
(registers). System registers are Read-Write type data points.
Note: Many System Registers are preassigned a function.
Index and Value Registers (Word)
The Index Register data type is represented by an “XR” prefix (e.g. XR1, XR2 etc.). There are 4 XR memory
locations available in EZ3-TouchPLC Modular. “XR” is a Read- Write data type and it is mainly used to point to
the correct address of “R” registers. The pointed-to “R” registers data value is stored in “#R” registers.
Value Register data type is represented by a “#R” prefix (e.g. #R1, #R2 etc.). There are 4 #R memory locations
available in EZ3-TouchPLC Modular. “#R” is a Read-Write data type and it is mainly used to read/write value of
“R” registers as pointed out by “XR” registers.
Both XR and #R registers are used in conjunction with each other and provide a convenient way of addressing R
registers.
Example:
Let's assume data values: R59=9874, R8000=32 If XR1=59
Then #R1=9874 (the actual data value of R59) If XR2=8000
Then #R2=32 (the actual data value of R8000)
XR contains the address of the operand (or specifies a register that contains the effective address), #R is used
to read or write the actual operand. Indirect addressing is often combined with pre- or post-increment (or
decrement) addressing. This allows the address of the operand to be increased or decreased by the specified
number either before or after using it. Proper usage of XR variables often saves a lot of programming.
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