VEGA VEGACOM 557 Profibus DP - Manual (Page 26)

26 VEGACOM 557 Profibus DP
6 Operating mode VEGACOM 557
Operating mode VEGACOM 557
Two different operating modes ar e available
for VEGACOM 557.
Depending on the operating mode, VEGA-
COM 557 reserves a different number of
input and output bytes in the Profibus-Mas-
ter.
6.1 Mode 50E2A
In this mode, VEGACOM 557 reserves 50
input bytes and 2 output bytes.
The Profibus-Master has to process 50 Bytes
of data consistently .
How it works
A control command and a block number (1
byte each) are written into the 2 Byte output
data. After VEGACOM 557 has received
these two Bytes via Pr ofibus DP, it answers
by sending the data of the required block -
these 50 Byte are then available to the Profi-
bus-Master as input bytes.
Since a maximum of 255 PC/DCS values and
up to 32 relay status are available in VEGA-
COM, but only 50 bytes at a time can be
transferred on the Profibus, the data are
multiplexed on the bus.
To facilitate this, the data ar e divided in
VEGACOM 557 into blocks. The requested
block can be enquired by the Profibus-Mas-
ter with the control command and the block
number.
8 PC/DCS values (6 Byte each), the control
command (1 Byte) and the block number (1
Byte) decremented by the value 1 are re-
turned in a block.
6.2 Mode 6E6A
In this mode, VEGACOM 557 reserves 6
input byte and 6 output byte.
The Profibus-Master must process 6 Byte
data consistently.
How it works
A control command and a PC/DCS value
number (1 Byte each) is written by the Profi-
bus-Master into the 6 Byte output data, the
remaining 4 Byte must be filled with the value
0xFF.
After VEGACOM 557 has received these 6
Byte via the Pr ofibus DP, it answers by send-
ing the data of the enquired PC/DCS value.
These 6 Byte are then available as input
bytes to the Pr ofibus-Master.
Since a maximum of 255 PC/DCS values and
up to 32 relay status are available in VEGA-
COM, but only 6 bytes at a time can be
transferred on the Profibus, the data on the
bus are multiplexed.
To facilitate this, the data in VEGACOM 557
are divided into single PC/DCS values. With
the control command and the PC/DCS value
number, the Pr ofibus-Master can enquir e t he
respective PC/DCS value.
6.3 Selection of the operating mode
To select the operating mode, it is necessar y,
to choose the respective configuration when
creating the bus configuration. The GSD file
provides both operating modes as options.
The selection is made with the respective
configuration tool, e.g. HW-Config for SIE-
MENS S7 systems or COM PROFIBUS for
SIEMENS S5 systems.
Depending on the configuration tool, a win-
dow is opened in which the desired operat-
ing mode can be selected when adding a
VEGACOM 557 slave to the bus configura-
tion.