Mitsubishi Electric Melsec Q Series User Manual page 244

APPENDIX
(Communication request
source station)
App - 6
(2) Executing the READ instruction using 3 channels and monitoring
devices with a programming tool
destination station)
READ instruction
3 channels used
(a) Calculating arrival monitoring time
Apply the following values for sequence scan time of the CPU module on
the communication request source station (St) and response time of the
CPU module on the communication request destination station (Rt).
St = 20ms
Rt = 30ms × 4 scans = 120ms
Since the READ instruction is used, communication processing time
between the Ethernet modules on the communication request source
station and on the communication request destination station (Dt) will be
the following value.
Dt = 9.9ms
Set a value larger than the following to the arrival monitoring time.
St × 2 + Dt + Rt = 20 × 2 + 9.9 + 120 = 169.9ms
POINT
In this processing, the READ instruction is executed using 3 channels and device
monitor is performed. Therefore, the maximum 4 scans may be required. (30ms × 4
scans = 120ms)
However, the processing can be performed in one scan by the following setting
(30ms × 1 scan = 30ms).
• Service processing setting (Universal model QCPU, LCPU)
• Time reserved for communication processing (SD315) (other than the Universal
model QCPU, LCPU)
(Example)
Arrival monitoring time when service processing is set to 4 times:
St × 2 + Dt + Rt = 20 × 2 + 9.9 + 30 = 79.9ms
For details on the setting, refer to the User's Manual (Function Explanation,
Program Fundamentals) for the CPU module used.
(b) Number of resends
Set 3 times.
(Communication
request
Device monitor
MELSEC-Q/L
(Communication request
source station)
Programming tool
App - 6