Hitachi HIDIC EH-150 Applications Manual page 22

[4] Restrictions on total drop line length
The total drop line length refers to the length obtained by adding up the length of all the drop lines
within one network.
The following restrictions are applied are on the total drop line length depending on the communication
speed:
125 kbps: 156 m max.
250 kbps: 78 m max.
500 kbps: 39 m max.
Device Tap Device Tap
(Note)
1m
6m
Device Tap
Device
2m
1m
(Note) With a
termination resistor
2m
In the configuration example above, the length of each drop line is within 6 m and causes no problem,
but the total length of all the drop lines becomes 42 m. This is longer than the restriction on the total
drop line length of 39 m at a communication speed of 500 kbps. Therefore, a communication speed of 125
kbps or 250 kbps should be used.
Device Tap
2m 2m
6m
Device Device
Device
Device
Device
Device
3-6
Chapter 3 System Configuration
Device Tap Device Tap
2m
6m
Device Device
Device Tap
Device Tap
2m
Device 6m
Device
2m
Device
(Note)