Accessing A "Slice" Of A Tagged Data Type - Siemens S7-1200 System Manual

4.4.10

Accessing a "slice" of a tagged data type

PLC tags and data block tags can be accessed at the bit, byte, or word level depending on
their size. The syntax for accessing such a data slice is as follows:
● "<PLC tag name>".xn (bit access)
● "<PLC tag name>".bn (byte access)
● "<PLC tag name>".wn (word access)
● "<Data block name>".<tag name>.xn (bit access)
● "<Data block name>".<tag name>.bn (byte access)
● "<Data block name>".<tag name>.wn (word access)
A double word-sized tag can be accessed by bits 0 - 31, bytes 0 - 3, or word 0 - 1. A word-
sized tag can be accessed by bits 0 - 15, bytes 0 - 1, or word 0. A byte-sized tag can be
accessed by bits 0 - 7, or byte 0. Bit, byte, and word slices can be used anywhere that bits,
bytes, or words are expected operands.
Note
Valid data types that can be accessed by slice are Byte, Char, Conn_Any, Date, DInt,
DWord, Event_Any, Event_Att, Hw_Any, Hw_Device, HW_Interface, Hw_Io, Hw_Pwm,
Hw_SubModule, Int, OB_Any, OB_Att, OB_Cyclic, OB_Delay, OB_WHINT, OB_PCYCLE,
OB_STARTUP, OB_TIMEERROR, OB_Tod, Port, Rtm, SInt, Time, Time_Of_Day, UDInt,
UInt, USInt, and Word. PLC Tags of type Real can be accessed by slice, but data block tags
of type Real cannot.
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
PLC concepts
4.4 Data types
121