A5.3 Transfer Of Las - YOKOGAWA vigilantplant EJA Series User Manual

A5.3 Transfer of LAS

There are two procedures for an LM to become the LAS:
• If the LM whose value of [V(ST) V(TN)] is the smallest on a segment, with the exception of the current LAS,
judges that there is no LAS on the segment, in such a case as when the segment has started up or when the current
LAS has failed, the LM declares itself as the LAS, then becomes the LAS. (With this procedure, an LM backs up
the LAS as shown in the following figure.)
• The LM whose value of [V(ST) V(TN)] is the smallest on a segment, with the exception of the current LAS,
requests the LAS on the same segment to transfer the right of being the LAS, then becomes the LAS.
LM
Node address: 0x14
LAS
SlotTime = 5
LAS
LM LM
Node address: Node address:
0x15 0x16
SlotTime = 5 SlotTime = 5
Figure 2. Backup of LAS
To set up an EJA as a device that is capable of backing
up the LAS, follow the procedure below.
NOTE: When changing the settings in an EJA, add the
EJA to the segment in which an LAS is running. After
making changes to the settings, do not turn off the
power to the EJA for at least 30 seconds.
(1) Set the node address of the EJA. In general, use
an address from 0x14 to [V(FUN) - 1].
0x00
0x0F
0x10
0x13
0x14
V (FUN)
V (FUN) + V (NUN)
0xF7
0xF8
0xFB
0xFC
Portable-device address
0xFF
Figure 3. Node Address Ranges
(2) In the LAS settings of the EJA, set the values of
V(ST), V(MRD), and V(MID) to the same as the
respective lowest capability values in all the
devices within the segment. An example is shown
below.
Basic device
Node address: Node address:
0xF1
Not used
Bridge device
LM device
Not used
V (NUN)
Basic device
Default address
FA0503.EPS
In the event that the current LAS in
this segment (node address 0x14)
fails, the LM with the address of 0x15
takes its place to become the LAS.
Basic device Basic device
Node address:
0xF2 0xF3
DlmeBasicInfo (EJA Index 361 (SM))
Sub-
Element
index
1 SlotTime
MaxResponse
3
Delay
MinInterPdu
6
Delay
In this case, set SlotTime, MaxResponseTime, and
MinInterPduDelay as follows:
ConfiguredLinkSettingsRecord (EJA Index 369 (SM))
Subindex
1 SlotTime
3 MaxResponseDelay
6 MinInterPduDelay
(3) In the LAS settings of the EJA, set the values of
V(FUN) and V(NUN) so that they include the
node addresses of all nodes within the same
segment. (See also Figure 3.)
ConfiguredLinkSettingsRecord (EJA Index 369 (SM))
Subindex
4 FirstUnpolledNodeId
7 NumConsecUnpolledNodeId
A-25
APPENDIX 5. Link Master Functions
Basic device
Node address:
0xF4
FA0502.EPS
Device Device Device
EJA
1 2 3
4 8 10 20
3 6 3 5
4 8 12 10
Setting
Element
(Default)
20 (4095)
6 ( 5)
12 ( 12)
Element Default Value
0x25
0xBA
Description
Capability value
for V(ST)
Capability value
for V(MRD)
Capability value
for V(MID)
TA0501.EPS
Description
V (ST)
V (MRD)
V (MID)
TA0502.EPS
Description
V (FUN)
V (NUN)
TA0503.EPS
IM 01C22T02-01E