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EM-7817-A Rev.2 P. 7 / 7
TIMING AT DATA COMMUNICATION
In this module, the transmission between CC-Link and HLS is not synchronized. Therefore, if one of the networks read the
transmitted data before the completion of its update by the other network, the data may be uncertain as 16-bit data. If the
correct 16-bit data is necessary, arrange the host application program.
For example, the initial data transmitted from HLS to CC-Link is 0000 | 0000 | 0000 | 0000 (T
0
). When the HLS changes
the data to 0000 | 0000 | 0000 | 0111 at THA, and CC-Link read it simultaneously (T
CA
= T
HA
), the 3 LSBs are uncertain at
the moment. The 3 LSBs are possibly 000, 001, 010, 011, 100, 101 or 110. When the HLS does not change the data until the
CC-Link reads it next time (T
CA
+1), the CC-Link can read correctly. When the CC-Link transmits and HLS reads data, they
do the same with the above.
When the 16 bits are independent data (e.g. discrete I/Os), the above phenomenon seems as the delay of 1 scan time. When
the 16-bit data is one word or the combinations of the bits have certain definition, you must be careful.
In order to avoid reading uncertain as 16-bit data, arrange the host application program. For example, the transmitting net-
work does not change the data longer than receiving network’s update time. The receiving network reads at least twice and
until the two sequential data sets are identical.
HLS
Update Timing
HLS Transmitting Data
CC-Link Receiving data
CC-Link
Update Timing
T
0
0000 | 0000 | 0000 | 0000
T
0
:
:
:
T
HA
0000 | 0000 | 0000 | 0111
0000 | 0000 | 0000 | 0xxx
T
CA
The LSBs of T
CA
are uncertain.
T
HA+1
0000 | 0000 | 0000 | 0111
T
HA+2
0000 | 0000 | 0000 | 0111
T
HA+3
0000 | 0000 | 0000 | 0111
T
HA+4
0000 | 0000 | 0000 | 0111
0000 | 0000 | 0000 | 0111
T
CA+1
Receives the correct data.
T
HA+5
0000 | 0000 | 0000 | 0111
T
HA+6
0000 | 0000 | 0000 | 0111
T
HA+7
0000 | 0000 | 0000 | 0111
T
HA+8
0000 | 0000 | 0000 | 0111
0000 | 0000 | 0000 | 0111
T
CA+2
CC-Link received data is fixed.
:
:
:
:
