8-3
Section
Data Link I/O Response Time
121
8-3-1 Computer to PC
In the following diagram illustrating the maximum data link I/O response time, a
CS1-series PC is used for the PC (#2) and the PC’s cycle time is greater than or
equal to the communications cycle time.
User application
Computer at node #1
(ClkWriteDatalink)
(*)
Send processing (FinsGateway)
Late
Communications
cycle time
Data link transmissions
I/O refresh
Data exchange
PC at node #2
1 cycle
Output ON delay
Data link I/O response time
Output device
There are two points shown in the diagram above where processing is delayed.
1, 2, 3...
1. Data exchange occurs just after the computer at node #1 passes the token
that makes it the polling node, causing a delay of up to one communications
cycle time before the data is transferred in data link processing.
2. The data transferred in data link processing arrives at the PC at node #2 af-
ter data exchange, so the data will not be read into the PC until the next data
exchange, causing a delay of up to one cycle. (If the cycle time of the PC at
node #2 is longer than the communications cycle time, the delay would be
approximately two cycles.)
The maximum number of words that can be transferred in one data exchange is
3,700 words for the CVM1 and CV-series PCs and 7,800 words for the CS1-se-
ries PCs.
Note
1. Noise may increase I/O delays.
2. The data send processing time for the area marked by the asterisk (*) in the
diagram will be affected by the processing capacity of the computer that is
used.
3. The communications cycle time may fluctuate.
4. For details regarding the time required for data exchanges between the
Controller Link Unit and the PC, refer to the Controller Link Units Operation
Manual (W309).
