Address Syntax

The new Syntax has the following motivation

Be more familiar with the TIA Syntax well known by S7 programmers
Add Type Information to support all available TIA types
"Type inference" to be not too verbose

Syntax

%{data-area-code}.D{bit-length-code}{byte-offset}(.{bit-offset})?

The parts are:

data-area-code:
bit-length-code:
byte-offset
bit-offset

Type identifier Postfix

Generally the TIA Syntax is used:

BOOL, INT, UINT, REAL

Furthermore the follwoing modifiers to the base types are used:

S = Short

D = Double

L = Long

Examples are:

SINT
USINT
DINT
LREAL
LINT
ULINT

Strings

Please see https://support.industry.siemens.com/tf/WW/en/posts/string-data-type/51621?page=0&pageSize=10

A short description of the syntax and intern format is found here PLC4X > Julians Proposal (S7 Driver Redesign) > String%20data%20type%20format.jpg .

The following Syntax is valid and will be supported:

STRING[n] // String with max number of characters: n
STRING // equivalent to STRING[254]

Note that a 2 byte prefix is used, so n+2 bytes have to be read from the plc.

The first byte represents the max length of the String, i.e., n above. The second one represents the actual length, i.e., the number of bytes to convert to string (starting from offset 2, then).

All bytes represent ASCII Chars.

Examples for valid addresses

%DB3.DX4.1
%DB3.DX4.1:BOOL
%DB3.DB4:INT
%DB3.DB4:UINT
%DB3.DW4:REAL