118 JVL Industri Elektronik A/S - User Manual - Ethernet for MAC and MIS motors
5.2 Protocol specifications
5.2.2 Ethernet POWERLINK
®
frame structure
POWERLINK messages are encapsulated in Ethernet II frames. The length of the frame
is restricted to the configured size, in order to guarantee the cycle time. Ethernet frames
have a minimum length of 64 bytes and a maximum of 1518 (exclusive preamble). The
Ethernet POWERLINK header contains only 3 bytes. Message type, destination ID and
Source ID. That leaves up to 1497 bytes of payload.
5.2.3 Ethernet POWERLINK CN State machine
In Ethernet POWERLINK, a Controlled Node starts up by a common initialization pro-
cess. All the states are valid when the device is powered and they are sub-states of the
NMT_GS_POWERED superstate.
NMT_GS_INITIALISATION
After system start, the device automatically assumes this state and network function-
ality begins. NMT_GS_INITIALISATION and all its sub-states are only internal states
of the device. In the NMT_GS_RESET_CONFIGURATION sub-state, the node ad
-
dress of the device is identified and it is determined whether it is configured as a MN
or CN. The JVL MAC00-ELx is a CN and thus, it enters the NMT CN state machine
in the NMT_GS_COMMUNICATING super-state.
NMT_GS_COMMUNICATING
NMT_CS_NOT_ACTIVE
This is a none-permanent state that allows a starting node to recognize the cur-
rent network state. Time out for SoC, PReq, PRes and SoA frames trigger the
device to enter state NMT_CS_BASIC_ETHERNET.
The NMT_CS_PREOPERATIONAL_1
Transition from NMT_CS_NOT_ACTIVE to NMT_CS_PRE_OPERATION-
AL_1 is triggered by a SoA or SoC frame being received. In this state CN may
send a frame only if the MN has authorized it to do so by a SoA command. There
is no PDO communication in this state. Receiving a SoC frame triggers the tran
-
sition from NMT_CS_PREOPERATIONAL_1 to NMT_CS_PREOPERATION-
AL_2.
The NMT_CS_PREOPERATIONAL_2
In this state PReq and PRes data may be invalid because PDO mappings may dif-
fer. In NMT_CS_EPL_MODE, error recognition (for example, loss of SoC or
PReq) always triggers the transition to NMT_CS_PREOPERATIONAL_1.
The NMT_CS_READY_TO_OPERATE
In this state, the CN signals that it is ready to operate to the MN. It responds to
the PReq query of the MN by sending a PRes frame.
The NMT_CS_OPERATIONAL
NMT Start Node command triggers the transition from
NMT_CS_READY_TO_OPERATE to the NMT_CS_OPERATIONAL. This is
the normal operating state of the CN.
TT3036GB
Preamble Ethernet header
8 bytes 14 bytes
Message
type
1byte
POWERLINK header
Dest.
ID
Source
ID
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