Emerson PACSystems RX3i, User Manual

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RSTI-EP PROFINET I/O Controller User Manual Section 6
GFK-2571R May 2021
Redundant Media 133
part of the PAC Machine Edition hardware configuration. (For example, the default test
packet timeout interval is 20 ms × (3+1) = 80 ms.)
Each device in the ring must be able to detect the failure or recovery of a connection. When
using third-party devices in a redundant media ring, failover time will be affected by the
performance of these devices. For devices that do not detect the failure or recovery of a
connection via LinkUp/LinkDown indication, the shortest guaranteed failover time will be
the test packet timeout interval, as described above.
For bumpless network recovery (without disturbing I/O communications to an I/O Device),
the Update Rate for the I/O Device should be configured to be greater than 1/2 of the
network recovery time. This permits the ring to be disconnected or reconnected without
timing out the communication connection between the I/O Device and its I/O Controller.
1000Base-T SFPs on a PNC001 module can introduce significant network recovery time. For
best MRP performance with a 10/100/1000 Mbps copper Ethernet MPR ring network,
configure the RJ45 Ethernet ports (Ports 1 and 2) as MRP ring ports instead of those SFP ports
(Ports 3 and 4) with 1000Base T SFPs.
Note:
The 1000BaseT SFPs qualified for use with the RX3i PNC001 module can only detect a
ring break when running at 1 Gbps at the IEEE 802.3 Clause 40 standard requirement of
750ms. In order to experience bumpless I/O at a 16ms I/O Update rate with these SFPs at
1 Gbps, the MRM must be configured with a Test Packet Interval of 10ms and a Test
Packet Count of 2.
6.1.2 Bumpless Operation with MRP
The PROFINET Controller supports bumpless operation with Emerson PROFINET I/O Devices
if and only if specific conditions are met. Bumpless operation means that a single break in
an MRP ring will not cause the PROFINET connection to be lost and there is no observed loss
and addition of PROFINET I/O Devices while the ring network recovers.
Without bumpless MRP, when a device is lost, it must be re-acquired by the I/O Controller;
a typical recovery time is on the order of seconds.
There are two ways an MRM detects a break in the ring:
• A message from an MRC that provides LinkUp/LinkDown detection
• Use of a test packet timeout interval
A network using Media Redundancy Protocol recovers from a ring failure within 80
milliseconds when running at 100/1000 Mbps full duplex with default Media Redundant
Manager (MRM) test packet values. Actual failover time depends on the device
responsiveness to network disconnection and reconnection, number of devices in the ring,
media speed, length of media, and frequency of sending test frames over the network.
Network recovery time is shorter with fewer devices, faster media speed, and shorter media
lengths. Third-party devices in the MRP ring may introduce additional network recovery
time. Network recovery time is limited by the ring participant with the slowest ring failure
recovery time. Devices that do not provide LinkUp/LinkDown detection should be
considered when calculating network recovery time.