Cycle Time - Balluff BIS M-4A3-082-401-07-S4 Anleitung

BIS M-4A_-082-401-07-...
Industrial RFID-System BIS M
2
IO-Link Basic Knowledge
2.1 General
IO-Link integrates conventional and intelligent sensors and
actuators in automation systems and is intended as a
communication standard below classic field buses. Field-
bus-independent transfer uses communication systems
that are already available (field buses or Ethernet-based
systems).
IO-Link devices, such as sensors and actuators, are
connected to the controlling system using a point-to-point
connection via a gateway, the IO-Link master. The IO-Link
devices are connected using commercially available
unshielded standard sensor cables.
Communication is based on a standard UART protocol
with a 24-V pulse modulation in half-duplex operation. This
allows classic three-conductor physics.
2.2 Protocol
With IO-Link communication, permanently defined frames
are cyclically exchanged between the IO-Link master and
the IO-Link device. In this protocol, both process and
required data, such as parameters or diagnostic data, is
transferred. The size and the type of the frame type and
the cycle time used result from the combination of master
and device features (see communication properties in
section 3.2 on page 7).
2.3

Cycle Time

The cycle time used (master cycle time) results from the
minimum possible cycle time of the IO-Link device
(min cycle time, see section 3.2 on page 7) and the
minimum possible cycle time of the IO-Link master. When
selecting the IO-Link master, please note that the larger
value determines the cycle time used.
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2.4 Process Data Flow
The data transfer is based on the general profile
specification (IO-Link Common Profile 1.0, see Fig. 2-1 for
example).
PDinput data stream (device view)
Transmission
direction
n n+1
("to master")
39 30 31 24 15
...
Byte 0 Byte 1
7 0 7 0 7
Integer16 UInteger8
"PDV2" "PDV1"
PVinD 3 PVinD 2
Data type: IntegerT Data type: UIntegerT
TypeLength: 16 TypeLength: 8
Bit offset: 24 Bit offset: 8
Example PDinput data stream
Fig. 2-1: Example of a PDinput data flow
The highest value byte (MSB, designated as Byte 0 ) is
transferred first and can be found in the PLC under the
lowest storage address. The lowest value byte (LSB) is
transferred last and has the highest byte number
(designated in Fig. 2-1 as Byte 4).
For word-based data types (> 8 bit) this means that the
byte at the lowest address is the highest value byte, while
the highest address contains the lowest value byte.
In the IODD, the description of the data flow is realized
using the skew descriptors. This skew starts at the right
with the lowest value byte.
Process data variables (in Fig. 2-1: PDV1, PDV2) are
aligned to the byte limits in most cases.
Binary information (BDC) is transferred in the lowest value
byte in most cases.
n+3 n+4 memory address in the PLC
n = baseaddress
8 7 0 Bit offset
Byte 3 Byte 4
0 7 0 Byte stream
Bool
"BDC1_2"
PVinD 1
Data type: Bool
TypeLength: 2
Bit offset: 0
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