User manual

905U-G Wireless Gateway User Manual
Page 23 ©September 2004
2.4.2 Profibus
The Profibus port has auto-detect of baud rate from 9600 bits/sec to 12Mbit/sec - no
configuration is required.
The Profibus units have internal hardware comprising the Profibus Interface. The Profibus
Interface handles all Profibus DP Network communications. The internal Radio Interface is
separate to the Profibus Interface, and handles all radio communications. I/O in the Radio
Interface is linked to I/O in the Profibus Interface in a flexible way via ESeries Configuration
Software.
The Profibus Slave interface provides a total of 416 I/O bytes, with a maximum 244 input
bytes and maximum 244 output bytes. A Profibus byte can contain 8 discrete (binary)
values, or two bytes can be used for a 16-bit analogue or pulse register. So the Profibus
interface is limited to 1952 discrete inputs or 122 analogue inputs or a combination. The
same applies for outputs.
For example, a Profibus host wants to read 800 discrete inputs (100 bytes) and write 400
discrete outputs (50 bytes). This will take up 150 bytes of the Profibus Interface, leaving 266
left. The remaining bytes could be used for 133 analogue I/O - up to 72 analogue inputs
(244 – 100 discrete input bytes) plus 61 analogue outputs - or vice-versa.
The Profibus Master interface provides a total of 2048 input bytes and 2048 output bytes. A
byte can contain 8 discrete (binary) values, or two bytes can be used for a 16-bit analogue or
pulse register. So the interface is limited to 4300 discrete inputs (the limit of the 905G
database) or 1024 analogue inputs (the limit of the HMS interface) or a combination. The
same applies for outputs.
2.4.3 Ethernet
The Ethernet port automatically handles Ethernet communications at 10 or 100 Mbit/sec. An
IP address is entered so that other Ethernet devices can recognize the 905G.
The Ethernet units have internal hardware comprising the Ethernet Interface. The Ethernet
Interface handles all Ethernet Network communications. The internal Radio Interface is
separate to the Ethernet Interface, and handles all radio communications. I/O in the Radio
Interface is linked to I/O in the Ethernet Interface in a flexible way via ESeries Configuration
Software.
The Ethernet Interface provides a total of 2048 input bytes and 2048 output bytes. An
Ethernet byte can contain 8 discrete (binary) values, or two bytes can be used for a 16-bit
analog or pulse register. So the Ethernet Interface is limited to 4300 discrete inputs (the limit
of the 905G database) or 1024 analog inputs (the limit of the Ethernet interface) or a
combination. The same applies for outputs.
For example, an Ethernet host wants to read 500 analog inputs (1000 bytes). The remaining
input bytes (1548) could be used for 12,384 discrete inputs - but the 905G database is not
this big. Provided there are no outputs required, there could be 3800 discrete inputs (4300 –
500 analogs). If there are outputs required, then the number of discrete inputs available will
be further limited.
2.5 Radio System Design
Each wireless I/O system can have up to 95 unit addresses, although up to 255 905K module
can share the same unit address (refer to 905K User Manual).