Yokogawa AXFA14G/C - Manual (Page 83)

IM 01E20F02-01E A-24
APPENDIX 4. LINK MASTER FUNCTIONS
APPENDIX 4. LINK MASTER FUNCTIONS
A4.1 Link Active Scheduler
A link active scheduler (LAS) is a deterministic,
centralized bus scheduler that can control communica-
tions on an H1 fieldbus segment. There is only one
LAS on an H1 fieldbus segment.
An AXF 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 transmis-
sion 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.
A4.2 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
FA0401.EPS
Figure A4.1 Example of Fieldbus configuration-3 LMs on Same Segment