ELPRO 105U - Ethernet 105 G; The 105 G Structure

105U-G Wireless Gateway User Manual
Page 9© August 2003
An “input” is a value coming into the 105G via the data bus (that is, a value written to the
105G from the Profibus master). An output is a value going out from the 105G via the data
bus (a value read by the Profibus master).
So a Profibus 105G could handle up to 1952 (244 x 8) discrete inputs or 244 low resolution
analogue inputs or 122 (244 x ½) high resolution analogue inputs, or some combination in
between.
For example, a Profibus 105G can handle 400 discrete inputs, 240 discrete outputs, 90
analogue inputs and 60 analogue outputs (assume analogues are 16-bit). The number of input
bytes is 230 (400/8 + 90*2). The number of output bytes is 150 (240/8 + 60*2). The total
number of I/O bytes is 380. If the number of analogue outputs was increased to 90, then the
total output bytes would be 210 (240/8 + 90*2), and the total number of I/O bytes is 440 -
this exceeds the capacity of the Profibus interface.
1.1.3 Ethernet 105G
The Ethernet 105G provides several different types of Ethernet functionality:
♦ Modbus TCP. Modbus TCP uses Modbus as a base protocol within an Ethernet
communications structure. The 105G provides class 0, 1 and partially class 2 slave
functionality.
♦ EtherNet IP. EtherNet IP is the version of Ethernet used by Allen-Bradley devices. The
105G provides level 2 I/O server CIP (ControlNet and DeviceNet).
♦ Internet functionality. The 105G has 1.4Mbyte of non-volatile “flash” memory for
embedded web “pages” (dynamic HTTP), on-board file system, user downloadable web
pages thru FTP server, and email functionality (SMTP).
The Ethernet connection is a transformer isolated RJ45 connector, 10/100 Mbit/sec.
The Ethernet 105G I/O database has 4300 registers (each of 16 bit value), however the
Ethernet interface only supports 2048 input bytes and maximum 2048 output bytes. Each
byte can be 8 discrete inputs or outputs, but analogue or pulse I/O take up 1 byte for low
resolution values (8-bit) or 2 bytes for high resolution values (16-bit).
An “input” is a value coming into the 105G via the data bus. An output is a value going out
from the 105G via the data bus.
So an Ethernet 105G can handle up to 4300 I/O total, but analogue or pulse inputs are limited
to 2048 x 8-bit values or 1024 x 16-bit values. The same limit applies to outputs.
For example, an Ethernet 105G can handle 2000 discrete inputs and 500 analogue inputs
(assume analogues are 16-bit). The number of input bytes is 1250 (2000/8 + 500*2). The
same unit could handle 4000 discrete outputs and 750 analogue outputs. The number of
output bytes is 2000 (4000/8 + 750*2). The total number of I/O is 3250 which is less than the
total limit of 4300.
1.2 The 105G Structure
The 105G has three functional sections:
• An I/O database (or "Process Image") maintains the latest values of all I/O in the wireless
I/O system. The I/O database comprises 4300 x 16 bit I/O registers and 4300 x 16 bit