Specifications

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Technical Description Section 9-2
9.1 General Information
The operating terminals allow for a simple connection to the Allen-Bradley PLCs.
The operating terminal is connected to the interface of the respective PLC-module.
The data communication on the interface is handled by the DF1 protocol.
Communication is possible with any system implementing the DF1 protocol (e.g.:
MicroLogix 1000-Series, SLC500 with SLC5/03, SLC500 with SLC5/04, PLC5 and
PLC5/250).
The software components of the system are fully adapted to the parameters and
marginal conditions of the PU interface.
This offers the user the following advantages:
- Random write and read access to the defined data file.
- The operating terminal automatically polls the freely definable data areas for
cyclic data.
- No configuration required within the PLC.
- The PU protocol is handled entirely by the firmware of the PLC. A PLC program
(function blocks, etc.) in the PLC is not required for the handling of the communi-
cation.
- The protocol provides error control. Transmission errors are detected and, if
possible, eliminated by repeating the transmission.
- The parameters of the interface SER1 are assigned in the programming soft-
ware in a protocol-specific manner and are stored in the Application description.
Modifying of the parameters is also possible in the setup mask or each other I/O
mask of the terminal at any time.
- The programming system provides a maximum of support to the operator in
programming the operating terminal. The definitions (abbreviations) used here
are identical with the definitions used within the PLC programm.
9.2 Technical Description
The interfacing of the operating terminal to the Allen-Bradley PLCs is effected in
full-duplex mode.
The DF1 protocol allows random read and write access to the defined integer num-
ber file in either bit or word-mode.
Before individual bits of a word can be accessed for a write operation, a read ac-
cess to the corresponding word must occur. After having modified the respective bit
as desired, the word is transmitted to the PLC. Therefore, special care must be
taken when accessing bits to ensure that the terminal and the PLC do not modify
individual bits within a word at the same time.