Specifications

CP143 H1 / TCP/IP manual Software
Rev. 00/07 5-21
5.7.6 Important considerations when using real-time clock functions
Here follow the most important considerations that you should take into account when using the
real-time clock functions:
• use consistent cycle times for SYNC messages
• use a consistent format for time
• the format for time must be MMS when you are employing CPs from VIPA as well as
Siemens.
• byte 6 of the ethernet address of every CP must be different, otherwise it could happen that
two CPs would attempt to become master simultaneously and therefore block the System.
• byte 6 of the ethernet address of the time transmitter must be 00h to guarantee that the time
transmitter is always the master.
5.7.7 Setting and interrogating the clock from the PLC
CP communications with the PLC is interrupt controlled and occurs via the Dual Port RAM. Job
number 218 is set aside for time-related processing in the PLC.
A SEND using this job number initiates a write operation and a RECEIVE initiates a read operation
for the time of the CP.
The respective time value is transferred by means of data words.
The status message is returned in an indicator word.
Configuration of data words for transferring data from the clock (6 DW):
10s 1s 1/10s 1/100s DW0
xx 10h 1h 10m 1m DW1
10D 1D day of week ---- DW2
10Y 1Y 10M 1M DW3
---- 1/1000s v—k kkkk DW4
10Jh 1Jh ssss --em DW5
15...12 11...8 7...4 3...0 Bit
Indicator word (ANZW) configuration for the transfer of the status:
Byte 1 Byte 0
0000 clock-
status
0000 xxB1B0
B1 B0 Clock may be set Clock can be read
00 yes no
01 yes yes
1 0 no no
1 1 no yes