GE P485 instruction manual Data exchange, Overview

GE Consumer & Industrial

P485 Modbus to Profibus

Converter

Chapter 3: 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 3–2for 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.

Internal Memory Buffer

	Input data
	(up to 244 bytes)
Sub Network	Output data	Fieldbus
	(up to 244 bytes)
	General data
	1024 bytes

Figure 3-1: Internal memory buffer

P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE 3–1