User`s manual

343
CHAPTER 14 DATA COMMUNICATIONS USING EXTERNAL DEVICE AND PROGRAMMABLE CONTROLLER CPU M : N
CONFIGURATION
14
14.3 Examples of Procedure for Data Communications with the Programmable Controller CPU
1. A slave station that wants to communicate data with the programmable controller CPU sends a
communications request to the master station to obtain the line usage right. A message structure
example is shown in step 2.
2. The master station transmits a permission granted response to the slave station that issued the
communications request.
: External device that obtained the line usage right
3. After communicating data with the programmable controller CPU within the maximum data
communications time from among the external devices, the slave station that received the
"permission granted" response goes to step 5.
4. The master station that transmitted the "permission granted" response and the slave stations that
did not obtain line usage right check the line usage time of the slave station that obtained the line
usage right and ignore receive data other than that addressed to their local station.
When the line usage time exceeds the maximum data communications time, each external device
performs the processing of step 7.
5. After data communications are complete, the slave station that exchanged data with the
programmable controller CPU transmits a communications complete report to the master station.
A message structure example is shown in step 6.
Slave stations that do not communicate data with the programmable controller CPU check if a
communications complete report was transmitted and do not communicate data with the master station
during that time.
*1
*1
(1B) (1C) (ZX) (CB)(2)(;)
(1B)
31H 42H
(1C)
31H 43H
(:)
31H 42H 31H 43H 5AH 58H 43H 42H32H3BH
3AH
(Y)
59H
Transmission destination station No. Transmission source station No.
Transmission destination station No. Transmission source station No.
Command Message wait Sum check code
Massage of 1
External device of
slave station that
wants to obtain the
line usage right
(1CH)
Master station
external device
(1BH)
Permission granted/ permission not granted
Massage of 2
Command "ZX" is a communications request
command for description purpose.
The user should select the command that
requests communications.
CPU
CPU CPU CPU
C24C24C24C24
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External device
(Station No.: 1BH)
(Station No.: 0H)
(Station No.: 1H) (Station No.: 2H) (Station No.: 15H)
External device
(Station No.: 1CH)
External device
(Station No.: 1DH)
External device
(Station No.: 1EH)
Mater station
(Before 6)
C24: Q series C24, QC24 (N), UC24
(After 6)
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