Chapter Two
Operation
MAN_105G_1.5
Page
18
2.4.1
Modbus / DF1
The user selects whether the 105U-G-MD1 should act as a Modbus Master or Modbus Slave
or DF1 device.
The data type and baud rate of the serial communications must be configured at the 105G to
match the host. Data types can be 7 or 8 bit, even/odd/no parity, with 1 or 2 stop bits. Data
rates can be 300 - 19200 baud.
The full 105G database (4300 registers) can be accessed by the Host Device.
2.4.2
Profibus
The Profibus port has auto-detect of baud rate from 9600 bits/sec to 12Mbit/sec - no
configuration is required. A Profibus slave address must be entered (1 – 126).
The Profibus port cannot access the full 105G database. The 105U-G-PF1 Profibus unit has
an internal HMS Anybus board to provide the Profibus interface. The Profibus port (that is,
the “host device”) communicates with the HMS board which communicates with the 105G
database. Links are configured linking the database I/O registers and the HMS Profibus I/O
bytes.
The HMS module 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 HMS 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 HMS 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.
2.4.3
Ethernet
The Ethernet port automatically handles Ethernet communications at 10 or 100 Mbit/sec. A
device IP address is entered so that other Ethernet devices can recognise the 105G.
The Ethernet port cannot access the full 105G database. The 105U-G-ET1 Ethernet unit has
an internal HMS Anybus board to provide the Ethernet interface. The Ethernet port (that is,
the “host device”) communicates with the HMS board which communicates with the 105G
database. “Data bus links” are configured between the database I/O registers and the HMS
Ethernet I/O bytes.
The HMS module provides a total of 2048 input bytes and 2048 output bytes. A Ethernet
byte can contain 8 discrete (binary) values, or two bytes can be used for a 16-bit analogue or
pulse register. So the HMS Ethernet interface is limited to 4300 discrete inputs (the limit of
the 105G database) or 1024 analogue inputs (the limit of the HMS interface) or a
combination. The same applies for outputs.
For example, an Ethernet host wants to read 500 analogue inputs (1000 bytes). The
remaining input bytes (1548) could be used for 12,384 discrete inputs - but the 105G
database is not this big. Provided there are no outputs required, there could be 3800 discrete
inputs (4300 – 500 analogues). If there are outputs required, then the number of discrete
inputs available will be further limited.
