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10. Profibus-DP guide
10.1 Profibus-DP Protocol overview
This chapter briefly introduces the Profibus-DP protocol. If you are familiar with this section, you can directly
read the communication configuration of Section 10.2.
10.1.1 Profibus-DP Introduction
Profuse is a fieldbus solution integrating H1 (process) and H2 (factory automation). It is an international, open
fieldbus standard and one of the eight fieldbuses in the international standard IEC61158. Profibus can spread digital
automation equipment from low-level (sensor/actuator) to intermediate-level execution level (cell level). According
to the application characteristics and different needs of users, Profibus provides three compatible version
communication protocols:FMS
、
PA and DP .
Profibus-DP Used for communication between unit level control devices and distributed I/O in automation
systems.
Profibus-DP Using Layer 1, Layer 2 and User Interface layers, Layers 3-7 are unused, and this streamlined
architecture ensures high-speed data transfer. The direct data link mapping program DDLM provides access to Layer
2. The user interface specifies the application functions of the device, the behavior of the Profibus-DP system and the
device. Profibus-DP is especially suitable for communication between PLCs and on-site hierarchical I/O devices. The
communication between the master stations is the token mode, the master-slave mode between the master station and
the slave station, and a mixture of the two methods.
10.1.2 Profibus-DP physical layer
1
、
Transmission medium.
PROFIBUS-DP transmission technology adopts RS485 transmission, and the transmission medium can select
two types of wires: type A and type B, A is a shielded twisted pair, and B is a common twisted pair. However, in the
EN50 170 standard, the type A wire is specified, and the type A has a larger extended length than the type B, as
shown in Table 6.
Table6
：
Line A Line B Description
Cable parameter
A type
B type
Characteristic impedance(
Ω
)
135~165Ω
(f＝3MHz~20MHz)
100~130Ω
(f＞100kHz)
Unit length capacitance(PF/m)
＜30pF/m
＜60pF/m
Loop resistance(
Ω
/km)
≤110Ω/km
-
Core cross-sectional area(mm2)
≥0.34mm2(22 AWG)
≥0.22mm2(22 AWG)
2
、
Transmission distance
The standard Profibus-DP supports the following transmission rates: (unit: kbps) 9.6, 19.2, 31.25, 45.45, 93.75,
187.5, 500, 1500, 3000, 6000, 12000. The input data and output data of each DP slave are up to 244B. When using
