Yokogawa EJA115 - Manual (Page 62)

IM 01C22T02-01E A-24
APPENDIX 5. Link Master Functions
APPENDIX 5. LINK MASTER FUNCTIONS
A5.1 Link Active Scheduler
A link active scheduler (LAS) is a deterministic, centralized bus scheduler that can control communications on an H1
fieldbus segment. There is only one LAS on an H1 fieldbus segment.
An EJA supports the following LAS functions.
• PN transmission: Identifies a fieldbus device newly connected to the same fieldbus segment. PN is short for Probe
Node.
• PT transmission: Passes a token governing the right to transmit, to a fieldbus device on the same segment. PT is
short for Pass Token.
• CD transmission: Carry out a scheduled transmission to a fieldbus device on the same segment. CD is short for
Compel Data.
• Time synchronization: Periodically transmits the time data to all fieldbus devices on the segment and returns the
time data in response to a request from a device.
• Live list equalization: Sends the live list data to link masters on the same segment.
• LAS transfer: Transfers the right to be the LAS on the segment to another link master.
A5.2 Link Master
A link master (LM) is any device containing a link active scheduler. There must be at least one LM on a segment.
When the LAS on a segment has failed, another LM on the same segment starts working as the LAS.
LM
Node address:
0x15
SlotTime = 5
LM
Node address:
0x16
SlotTime = 5
Node address: 0x14
SlotTime = 5
Basic device
Node address:
0xF1
Basic device
Node address:
0xF2
Basic device
Node address:
0xF3
Basic device
Node address:
0xF4
LAS
There are 3 LMs on this segment.
LM
FA0501.EPS
Figure 1. Example of Fieldbus configuration-3 LMs on Same Segment