# BASEstartm Open DAS
for Allen-Bradley Data Highwaytm
on Tru64tm UNIX
Installation and User's Guide

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## 3.3.2 PLC-3 Addressing Syntax and Supported Data Types

The PLC-3 family supports the following addressing syntaxes:

- Data table addressing
- Extended addressing

Section 3.3.2.1 and Section 3.3.2.2 describe these addressing syntaxes.

### 3.3.2.1 PLC-3 Data Table Addressing

The structure of a legal data table address for the PLC-3 differs depending on the table that is being addressed. The PLC-3 supports the following data table sections:

> I - Input
> O - Output
> C - Counter
> T - Timer
> A - ASCII
> B - Binary
> D - Decimal
> F - Floating-Point
> H - High-Order Integer
> N - Integer
> S - Status
> P - Pointer

Figure 3-2 shows the structure of a legal I/O data table address for the PLC-3.

Table 3-8 shows examples of legal I/O data table addresses for the PLC-3.

Figure 3-2 PLC-3 I/O Data Table Address Format

Table 3-8 Example PLC-3 I/O Data Table Addresses
Example Address | MMS Type1 | Description
--- | --- | ---
I20 | UNSIGNED_16 | Input image rack 2 group 0 octal
I377 | INTEGER_16 | Input image rack 37 group 7 octal
I1:1777/17 | BIT_STRING | Bit 17 of word 1777 octal in file 1 decimal
$O33:77/1 | BIT_STRING | Bit 1 of word 77 octal in file 33 decimal
O99:167 | INTEGER_16 | Word 167 octal in file 99 decimal
I0 | Array of 10 UNSIGNED_16 | Ten words beginning at rack 0 group 0

1Arrays are supported. Structures are not supported. Variable size arrays are not supported.

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