Reading Out Available Token Hold Time When Receiving The Token - Siemens SIMATIC S5 Manual

Start-Up, Tests, and Diagnostics
3.4.8

Reading Out Available Token Hold Time When Receiving the Token

(TIME_TTH_READ)
The TIME_TTH_READ service gives you the available token hold time when receiving the token.
It is very useful in the start-up phase for setting the target rotation time.
If the available token hold time moves towards zero, you must assign a higher value to the target
rotation time. Since the available token hold time fluctuates, you should read it out several times at
short intervals and calculate its mean value.
Structure the TIME_TTH_READ
request block as follows:
Request Block
Byte
0 com_class
FMA-Request=00
(service request)
1 user_id
Freely assignable ID. That ID is returned
unchanged in the confirmation.
2 service_code
Type of service requested:
TIME_TTH_READ=23
3-7
irrelevant
Relevant
parameters
* The values for the remaining token hold time can be in the range of 0 to 1 048 320 bit times.
Figure 3-15. Structure of the TIME_TTH_READ Request and Confirmation Blocks
link_status
Table 3-9. link_status Messages for the TIME_TTH_READ Confirmation
link_status Message
00
H
15
H
3-24
H
H
ok (okay): Positive acknowledgement, rest token hold time
was read out
iv (invalid): Error, local station is passive,
service is impossible
The data are stored in the TIME_TTH_READ
confirmation block as follows:
Confirmation Block
Byte
0 com_class
FMA-Confirmation=01
acknowledgment from firmware
(
following FMA_Request
1
user_id
ID assigned in the FMA_Request
2
service_code
Type of service provided:
TIME_TTH_READ=23
3 link_status
4-7
irrelevant
8
Remaining token hold time *
high word
(
9
Remaining token hold time *
(low word)
Significance
S5-95U, SINEC L2
H
)
H
)
EWA 4NEB 812 6112-02