NORD Drivesystems BU0090 - Manual (Page 26)

NORDAC AS-Interface Manual
26 BU 0090 GB
The AS interface system replaces the expensive parallel wiring of decentralised sensors (inputs) and actuators
(outputs) with a few bits (1-4 bits).
The AS interface options from Getriebebau NORD, which need to be supplied with an additional +24V DC
supply (AUX, black cable connection) for the electrical components, can also be used as I/O expansions for
customer-specific applications. An AS interface option can be used wherever more I/Os are required than are
available on the frequency inverters (i.e. onboard) or on the additional customer's interfaces. The black and
yellow AS-i standard cables are completely independent of each other, i.e. if the +24V DC voltage (AUX / black
cable) is switched off, the AS interface network (yellow cable) remains in operation and therefore supplies the
slave. Due to their special geometrically asymmetrical dimensions, both the yellow standard cable and the
optional black AS interface cable are mechanically protected against incorrect polarity.
The AS interface is a "single master / multiple slave system", i.e. there is only one master and several slaves in
an AS interface network. In the normal address mode, a maximum of 31 slaves can be integrated and
operated in an AS interface network with one master. With AS-i masters which support the extended address
mode, up to 62 slaves can be administered by a single master. Both the master and the slaves are connected
via the yellow standard AS interface cable. Both the master and the slaves are connected via the yellow
standard AS interface cable.
The AS interface master sends the same number of telegrams as the number of connected and active AS
interface slaves in the network. Each slave in sequence is cyclically addressed by these telegrams, starting
from the active slave with the lowest address.
For the master there are as many slave (addresses), as there are AS interface modules connected to the
network and activated. The response time of all active slaves is the data cycle time (approx. 5 ms for max. 31
slaves in standard mode). The response time is fixed or specified (real-time capability) and is proportional to
the number of activated slaves. Hence, e.g. the response time is halved for about half the number of slaves to:
5 ms * 15/31 = approx. 2.4 ms.
An AS interface master communicates independently with the AS interface slave modules which are
connected and addressed to the AS-i bus. It exchanges data with the individual slave modules. A master
coordinates all activities on the AS-i bus. An AS-i slave only communicates with the AS-i master on request by
the master. The AS-i slave passes on the requested information and signal statuses of the connected
peripherals (inputs, outputs...) to the master. A repeated telegram takes 150 µs and is included in the cycle
time of max. 5 ms (AS Interface network with S-7.4 slaves) or max. 21 ms (AS Interface network with S-7.A
slaves).
It is the task of the control unit (SPS, PC) and not that of the AS-i master to control the plant. However, at the
latest after 5ms or 21 ms (the maximum cycle time) the master detects whether a slave is no longer
responding (slave failure). The AS interface telegram is the message between the master and the slave in both
directions. First the initial data are sent (written) to the connected slave from the master, then the initial data
from the slave for each slave access and within a telegram are returned to the master (read).
Data exchange process:
The ASi data protocol provides 4 bits for the exchange of reference data.
During a cycle, each address (1 ... 31) is accessed once by the master. The master sends an order telegram
(with 4 Bit reference data) to the slave and immediately receives a corresponding response telegram (also with
4 Bit reference data).
For standard slaves (SK TUx-AS1) the maximum cycle time is therefore 5ms.
Master
Control unit
SL 1
1
SL 2
2
SL3
31
Master call up
Slave answers
SL 1
1