4-6. Communication Times
50
2. P/W PC Link Response Time
The P/W PC Link Response time is the time between an input transition at one station and the corresponding
output transition to another station.
In this section, the P/W PC Link Response Time is explained using the following example :
[EXAMPLE]
Station number 01
Station number 02
(UNIT NO. 01)
(UNIT NO. 02)
Programmable Controller
Programmable Controller
Program
Program
Synchronous with CPU
Asynchronous Synchronous with CPU
scan operation
operation
scan operation
In the above example, the operation flow from an input transition to an output transition is explained as follows :
Input transition
I/O Update
Program execution
PC Link buffer
update
Buffer update signal
Token reception
Data distribution
PC Link buffer
update
Program execution
I/O Update
The operation of station number 01
(UNIT NO. 01)
The operation of station number 02
(UNIT NO. 02)
Output transition
The external input realy X 0 in the Programmable
Controller 01 is turned ON.
At the time of I/O update in the CPU scan[station
number 01(UNIT NO. 01)], the X 0 status in taken into
CPU.
The external input relay X 0 turns ON and the L 0 turns
ON.
The buffer in the W Type(Wire) Link Unit at station
number 01(UNIT NO. 01) is updateed at the P/W PC
Link update time in the CPU scan, after the buffer is
ready to be updated.
To confirm the buffer availability, the buffer update
signal is transmitted during the link buffer update time.
When the first token is passed after the reception of the buffer update signal, the send area data in the buffer is prepared for
transferred.
The data are actually distributed during one transmission cycle time plus the transmission time needed for next station .
The data in the buffer at station number 02 is transferred
to the CPU memory.
The link relay L 0 turns ON and Y10 turns ON.
At the time of I/O update in the CPU scan[station
number 02(UNIT NO. 02)],the Y10 status is updated.
The external output relay Y10 in the Programmable
Controller 02 is turned ON.
X 0
L 0
L 0
Y10
