User's Guide; Jema Standard Compliance; Communication Times; Table 6-1 J.station Communication Time - Hitachi J.NET User Manual

6. User's Guide

6.1 JEMA standard compliance

For details, see 1.3 Support specifications for JEMA standard.

6.2 Communication times

For option modules including a J.NET module, each module updates its corresponding I/O data periodically
according to the communication time of each module. The CPU module prepares the I/O data updated by the
option module, and then uses the ladder program to control the option module. Because the ladder program runs
repeatedly at each constant cycle (sequence cycle) to avoid missing I/O data, the communication time of each
option module must be set to 1/2 of the sequence cycle.
The communication time of an option module depends on the communication word count setting of each option
module and the number of option modules mounted on the CPU unit. To calculate the communication time of a
J.NET module, use the following method. For details about how to calculate the communication time of an
option module other than a J.NET module, see the manual of the relevant option module.
● Communication time of a J.NET module
The communication time of a J.NET module is the sum of each slave device's communication time indicated in
the following formula. In other words, if slave devices connected to the J.NET module are assumed as slave
device 1, slave device 2, ... slave device n, the communication time is calculated as follows:
Communication time = Communication time of slave device 1
● If the module is connected to J.STATION
The communication time for one J.STATION depends on the transmission speed and the number of I/O points
assigned to the J.STATION. Use the following table to calculate the communication time.
Formula to find the
communication time for one
J.STATION
N: Number of I/O points
assigned to J.STATION)
● If the module is connected to a device other than J.STATION
For details about the communication time of devices other than J.STATION, see the instruction manual of your
device.
+ Communication time of slave device 2
+ Communication time of slave device n

Table 6-1 J.STATION communication time

Communication time = 1.85 + 0.0031 N [ms] (transmission speed 1 Mbps)
Communication time = 2.35 + 0.0054 N [ms] (transmission speed 0.5 Mbps)
Communication time = 3.45 + 0.0092 N [ms] (transmission speed 0.25 Mbps)
Communication time = 4.85 + 0.0176 N [ms] (transmission speed 0.125 Mbps)
6-1
6. User's Guide