Parker Hannifin
node of the example above, and the timing in the table below, the
time using a PIO-347 would be 12 milliseconds, and using a PIO-337
would be two milliseconds.
Node Type
Base time
(milliseconds)
time/digital point
(microseconds)
time/analog point
(microseconds)
PIO-347
5 100 270
PIO-337 1
15
40
Health Period and Node Health
Node health is a way for the master to periodically (known as the
Health Period) ascertain that all nodes are still alive, and to respond
appropriately if one goes “off line”. ACR9000 uses the Heart Beating
protocol for nodes that support it, and Node Guarding protocol for
other nodes. These are standard CANopen features. Compatibility is
determined automatically when the network is started. The Health
period is set to 10 times the Cycle Period.
Starting and Configuring the Network
An ACR9000 network master may start and reset the network at any
time. When the network is started via bit 11265, the ACR9000 initially
places all slave nodes into the “Pre-operational” state. During this
state, the ACR9000 interrogates and configures the slaves as
required. The slaves are then placed into the “Operational” state,
and automatic transfer between the slave’s physical I/O and the
ACR9000’s I/O parameters and bits takes place.
Before the network may become in the “Operational” state, the
master must know how many slave nodes there are, what the node
numbers are, and how many and what type of I/O are on each
node.
In some applications, the external nodes may be powered after
ACR9000, and hence not available for configuration on ACR9000’s
power up. For this reason, the ACR9000 user is required to explicitly
request network start via a control flag. The flag (bit 11265) is used
for starting the network. The flag is self-clearing (cleared
automatically by ACR9000 when the attempt to start the network
has completed). There are also status bits and parameters to
indicate the results of starting the network. Examples would be error
bits, bit rate, cycle period, node status, etc. A typical application
scenario would be as follows.
•
Perform application initialization, and dwell or otherwise
determine that external nodes are powered up.
•
Write to any required parameters if the values are not yet
correct.
•
Assert bit 11265 requesting I/O network start.
130 Programmer’s Guide
