Specifications

Head Station STL-PB1 (Profibus DP) Profibus DP
Quick Start Guide for the MELSEC STlite Series 2 - 7
2.2.6 Wiring
Since RS 485 transmission technology is used, all devices are connected in a line structure. To connect
the STL-PB1 to a Profibus DP network, use only the Profibus connector and shielded twisted pair Profi-
bus cable complying with EN50170. Cable type A is strongly recommended.
The maximum line length for a bus segment depends on the transmission speed.
When connecting the nodes, ensure that the data cables are not mixed up. To achieve high interfer-
ence resistance of the system against electromagnetic radiation, a shielded data cable (type A is
shielded) should definitely be used. The shielding is to be connected to the protective ground on
both sides ensuring good conductivity via large area shield clamps. Equipotential bonding of all con-
nected field devices is also recommended.
Stubs must absolutely be avoided with transmission rates greater than or equal to 1.5 MBit/s.
Parameter Specification
Tab. 2-3: Specifications for cable type A
Wave resistance 135 to 165 
Capacitance per unit  30 pF/m
Loop resistance  110 /km
Core diameter  0.64 mm
Core cross section  0.34 mm
2
Transmission speed
Max. bus segment
length
Tab. 2-4: Max. bus segment length
9.6 / 19.2 / 45.45 / 93.75 kbit/s 1200 m
187.5 kbit/s 1000 m
500 kbit/s 400 m
1.5 Mbit/s 200 m
3 / 6 / 12 Mbit/s 100 m
b
CAUTION:
When the Profibus cable is laid, do not lay it close to main circuits or power lines.
They should be installed 100 mm (3.9 inch) or more from each other. Not doing so could result
in noise that would cause malfunctioning.
Fig. 2-8: Connection of the Profibus cable
Profibus node
(e. g. STL-PB1)
3
8
RXD/TXD-P
RXD/TXD-N
From Profibus node
To Profibus node