PROFIBUS PA = PROFIBUS for Process Automation

1

• PROFIBUS PA PROFIBUS for Process Automation
• PA is based on the DP and DP Extended protocol
• DP Master Class 1 controls both DP AND PA field
  devices
• Definitions for DP protocol also valid for PA
• Parameterization
• Configuration
• Cyclic data exchange
• Diagnostic
• ...

2

• Physical Setup
• Physical layer based on IEC 1158-2
• Synchronous data transfer with Manchester coding
• Power AND data are transferred via the same wire
• Different components for the physical setup
  (cable, connectors, termination)
• Rules regarding topology and length according to
  IEC 1158-2
• Transmission rate is 31.25kbaud

3

• Physical Setup (continued) - Comparison

RS485 wire carries data only
IEC 1158-2 wire carries data and power
Physics
9,6K 19,2K 45,45K 93,75K 187,5K 1,5M 3M
6M 12M
31,25K
Transmission Rate
NRZ (No Return to Zero)
Coding
Manchester
11 bits per data byte 1 start bit, 8 data bits
(LSB first) 1 parity bit (even parity), 1 stop bit
8 bits per data byte 8 data bits (MSB first)
Character Format
1 parity bit for each character 1 byte FCS check
sum (Frame Check Sequence)
16 bit CRC (Cyclic Redundancy Check)
Check Sequence
4

• Message Structure

SD
LE
LEr
SD
DA
SA
FC
DU..
FCS
ED
SD
LE
LEr
SD
DA
SA
FC
DU..
CRC
EOF
P
SOF
P 16 Bit Preample SD Start Delimiter LE Net
Data Length (DU) DA, SA , FC, DSAP,
SSAP LEr Length repeated DA Destination Address
(Where the message goes to) SA Source Address
(Where the message comes from) FC Function Code
( FCType Priority of Message) DU Data Unit
(Up to 246 Bytes including 2 Bytes for
SAPs) FCS Frame Checking Sequence CRC 16 Bit
Cyclic Redundancy Check ED End
Delimiter EOF End Of Frame
5

• Character Format

6

• Network Addressing

PROFIBUS 45.45kbaud
PA Coupler
PA Coupler
24 V
PROFIBUS PA 31.25kbaud
7

• Network Topology

Spur Line
PROFIBUS
Star
(Main) Line
24 V
T Branch
PROFIBUS PA
Termination
8

• Network Topology (continued)

9

• Network Setup - Rules (continued)

PA Coupler
24 V
Up to 31 PA field devices can be connected to ONE
coupler
10

• Network Setup - Rules

Up to 5 couplers can be used with one link
PA Link
PA Coupler
11

• Network Setup - Rules (continued)

PA Link
PA Coupler
Up to 31 PA field devices can be connected to ONE
link - INDEPENDENT of the number of couplers
12

• Network Setup - Rules (continued)

PA Link
PA Coupler
Maximum current flow per coupler 400mA
for 110mA for EEx ib II C ignition
protection 90mA for EEx ia II C ignition
protection
I
13

• Network Setup - Rules (continued)

24 V
Maximum segment length per coupler 1,900m
14

• Network Setup - Rules (continued) (Allowed Length
  PER Drop/Spur Line)

15

• PA Profile
• Definition on the application layer level
• Profile defines variables, function blocks,
  meaning of the data, mapping to communication
  services...
• Devices with the same profile implemented can be
  exchanged
• Current version of PA Profile is V3.0
• Available as official PROFIBUS International
  document with order no. 3.042
• Pre-defined GSD files for various PA field
  devices available

16

• PA Profile (continued)

DP services cyclic and acyclic
Status
Measured value
Profile B
Measuring range
Filter time
(e.g. for pressure transmitters)
Alarm/warning limits
DP Services acyclic
Alarm summary
TAG
DP services acyclic
Manufacturer-specific parameters
17

• Electronic Data Sheets

GSD File for description of communication
parameters
PA Field Device
Device Description File for specification of
functionality
18

• Engineering Tool

PROFIBUS (up to 12 Mbaud)
Engineering Tool (Diagnostic Master)
Direct access to field device via DP Extensions
(e.g. to change range of measurement)
PROFIBUS-PA (31.25 kbaud)