P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE
3–1
GE Consumer & Industrial
P485 Modbus to Profibus
Converter
Chapter 3: Data exchange
Data exchange
Overview
DESCRIPTION
Data from the fieldbus (Profibus) and the sub network (Modbus) is stored in an internal
memory buffer. This is a easy method for data exchange where the fieldbus control
system simply reads and writes data to pre-defined memory locations, and the serial sub
network also use the same internal memory buffer to read and write data. Refer to Figure
3-2: Data exchange overview on page 3–2 for details.
INTERNAL MEMORY
BUFFER STRUCTURE
The internal memory buffer can be seen as a memory space with three different types of
data; input data, output data and general data.
•
Input data
: This is data that should be sent to the fieldbus. The P485 can handle up to
244 bytes of input data. The total input/output data must not exceed 416 bytes.
•
Output data
: this is data recieved
from
the fieldbus. The P485 can handle up to 244
bytes of output data.
•
General data
: This data
cannot
be accessed from the fieldbus, and is used for
transfers between nodes on the sub-network, or as a general “scratch pad” for data.
The P485 can handle up to 1024 bytes of general data.
Figure 3-1: Internal memory buffer
Internal Memory Buffer
Output data
(up to 244 bytes)
Input data
(up to 244 bytes)
Sub Network
Fieldbus
General data
1024 bytes
Summary of Contents for P485
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Page 36: ...4 14 P485 MODBUS TO PROFIBUS CONVERTER USER GUIDE SOFTWARE OVERVIEW ...
Page 42: ...5 6 P485 MODBUS TO PROFIBUS CONVERTER USER GUIDE COMMUNICATION MODEL ...
Page 56: ...8 6 P485 MODBUS TO PROFIBUS CONVERTER USER GUIDE ADVANCED FUNCTIONS ...
Page 74: ...10 2 P485 MODBUS TO PROFIBUS CONVERTER USER GUIDE MISCELLANEOUS ...
