User`s manual

340
1. When the system starts, the external device with the lowest station No. (1BH) is given the line
usage right.
2. The external device that obtained the line usage right,
a) When communicating data with the programmable controller CPU, begins processing from step 4 after
communicating data with the programmable controller CPU within the maximum data communications
time from among all the external devices.
b) When not communicating data with the programmable controller CPU, immediately begins processing
from step 4
3. The external devices that have not obtained the line usage right check the line usage time of the
external device that obtained the line usage right and ignore the receive data not addressed to
their own station.
When the line usage time exceeds the maximum data communications time, each external device
performs the processing of step 7.
: External device that obtained the line usage right
4. External devices that communicated data with the programmable controller CPU, or external
devices that do not have to communicate data with the programmable controller CPU, transmit the
data for transferring the line usage right to the external device of the next station No. A message
structure example is shown in Step 5.
When a response message (step 5) is not received from the next external device to which the line usage
right was passed, data transmission for transferring the line usage right to the external device of the next
station No. is repeated until the line usage right is accepted.
CPU
CPU CPU CPU
C24C24C24C24
§§
6
4
5
External device
(Station No.: 1BH)
(Station No.:0H)
(Station No.:1H) (Station No.:2H) (Station No.:15H)
External device
(Station No.: 1CH)
(Before 5)
C24: Q series C24, QC24 (N), UC24
Data communica-
tions with arbitrary
programmable
controller CPU
(Before 5)
External device
(Station No.: 1DH)
External device
(Station No.: 1EH)