Yokogawa EJA115 - Manual (Page 63)

IM 01C22T02-01E A-25
APPENDIX 5. Link Master Functions
A5.3 Transfer of LAS
There are two procedures for an LM to become the LAS:
• If the LM whose value of [V(ST)
ϫV(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)
ϫV(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:
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
LAS
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.
LM
FA0502.EPS
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].
Not used
LM device
Not used
Basic device
Default address
Portable-device address
V (FUN)
V (FUN) + V (NUN)
V (NUN)
0xFF
0xFC
0xFB
0xF8
0xF7
0x00
FA0503.EPS
0x0F
0x10
0x13
0x14
Bridge device
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.
Sub-
index
Element EJA
Device
1
Device
2
Device
3
Description
1
3
6
SlotTime
MaxResponse
Delay
MinInterPdu
Delay
4
3
4
8
6
8
10
3
12
20
5
10
Capability value
for V(ST)
Capability value
for V(MRD)
Capability value
for V(MID)
TA0501.EPS
DlmeBasicInfo (EJA Index 361 (SM))
In this case, set SlotTime, MaxResponseTime, and
MinInterPduDelay as follows:
Subindex Element
ConfiguredLinkSettingsRecord (EJA Index 369 (SM))
Description
Setting
(Default)
V (ST)
V (MRD)
V (MID)
20
6
12
(4095)
( 5)
( 12)
SlotTime
MaxResponseDelay
MinInterPduDelay
1
3
6
TA0502.EPS
(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.)
Subindex Element
ConfiguredLinkSettingsRecord (EJA Index 369 (SM))
Description Default Value
V (FUN)
V (NUN)
0x25
0xBA
FirstUnpolledNodeId
NumConsecUnpolledNodeId
4
7
TA0503.EPS