SERCOS III Technical Introduction
SERCOS Seminar, Atlanta
September 16, 2009
Evolution of SERCOS
Innovation by Combining Ethernet and SERCOS
SERCOS III
Hardware
SERCOS
Communication
Profile (SCP)
Function Specific
Profile (FSP)
SERCOS II
SERCOS Applications
…
Standard
IP
Applications
…
Servo &
Motion
Profile
RT-Data
SVC
Channel
Master
Slave
comm.
Safety
I/O´s
Drives
Innovation by
combination of
SERCOS and
Ethernet
Generic Device Profile GDP
2 RT Channel (P&S)
NRT-Channel
S/IP
Connections of
SVC
Producer
UDP/TCP
and
Consumer
IP
Sync
SERCON816
(optical
transmission)
SERCON100 Master or
SERCON100 Slave
Ethernet Dual PHY
2, 4, 8, 16 Mbit/s
(c) SERCOS International 2009
Ethernet
Sync
netX with
or
SERCOS III Master or
SERCOS III Slave
100 Mbit/s
No. 2
Topology
Topology
Line and Ring
Master
primary or
secondary channel
P1
Slave 1
P1
Slave 3
Slave 2
P2
P1
Line
P2
P2
P2
P1
secondary channel
primary channel
Slave 1
P1
Master
P1
Slave 3
Slave 2
P2
P1
Ring
P2
P2
P2
P1
Cyclic redundant transmission of
real-time data in primary and secondary channel
(c) SERCOS International 2009
No. 4
Topology (not permitted)
No switches, no hubs
Ethernet (Office)
Master
P1
P2
Switches or Hubs are not needed and are not
permitted as intermediate infrastructure components
within a SERCOS III network
RT Channel
I/O
(c) SERCOS International 2009
No. 5
Topology (not permitted)
Line with switch
S III Telegrams using broadcast address
Master
Standard
Switch
Ethernet (Office)
(c) SERCOS International 2009
No. 6
Communication Redundancy
with
Ring Topology
Redundancy
Ring break
S-Channel
master
P-Channel
Step 1
Ring OK
slave
n-1
slave n
Fast-Forward
Fast-Forward
S-Channel
master
Step 2
Ring break
P-Channel
slave
n-1
X
X
Loopback & Forward
(c) SERCOS International 2009
Communication
recovery time < 25 µs
slave
n
Loopback & Forward
No. 8
Redundancy
Ring recovery
S-Channel
master
Step 3
P-Link OK
S-Link OK
P-Channel
P-LINK
slave
n
slave
n-1
S-LINK
Loopback & Forward
Slave signals S-Link OK in ATn-P
Loopback & Forward
Slave signals P-Link OK in ATn-S
S-Channel
master
Step 4
Ring
recovery
P-Channel
slave
n-1
Master commands Fast-Forward
(c) SERCOS International 2009
slave
n
Master commands Fast-Forward
No. 9
Wiring
Cables
Connectors
Flexibility in wiring
P2<-->P1
P2<-->P2
P1<-->P2
P1<-->P1
 Each Slave has two Ports (P1 and P2)
 Port 1 and Port 2 are interchangeable
 No error can happen in wiring
 Simplification during commissioning
(c) SERCOS International 2009
No. 11
Flexibility in the choice of the cable type
 Useful for industrial applications, suitable for trailing
cable
 Cable type and Shielding
 min. CAT5e with S/UTP
 Industry: CAT5e with S/STP (SERCOS III)
 Use of Patch cable or Crossover cable possible
 Flexible in the choice of the cable type
 Simplification in commissioning
 Length 100m (max.)
 S III specifies ground connection of shielding
and unused wires
RJ 45
IP 20
 Recommendation of connectors and sockets
 Selection of certified components
 SERCOS III (RJ45 & M12, IP 20 & IP 67)
RJ 45, M12,
IP 67
(c) SERCOS International 2009
No. 12
Communication
and
Telegram structure
General telegram structure
S III Ethernet type = 0x88CD
S III HEADER
Preamble
SFD
Destination Source Ethernet
address address Type
7+1 Byte
6 Byte
6 Byte
MST
(S3H)
data field
2 Byte
FCS
4 Byte
IFG
 12 Byte
46-1500 Byte
checked via FCS
S III data

MAC layer: (overhead = 26 bytes)
 min. telegram length:
72 bytes  5,8 µs
 max. telegram length: 1526 bytes  122,1µs

Media layer: (overhead = 38 bytes)


min. telegram length:
84 bytes  6,8 µs
max. telegram length: 1538 bytes  123,1µs
 SERCOS III based on Standard Ethernet according ISO/IEC 8802-3
(c) SERCOS International 2009
No. 14
Communication Sequence in CP3/CP4
MDT0
MDT1
MDT2 MDT3
AT0
AT1
AT2
AT3
H M
D S
R T
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
ETH telegrams
H M
D S
R T
RT channel
NRT channel
(Ethertype = 0x88CD)
(Ethertype <> 0x88CD)
Communication cycle
MDT0
MDT1
MDT2 MDT3
H M
D S
R T
H S
D 3
R H
H S
D 3
R H
RT channel
ETH telegrams
H S
D 3
R H
NRT channel
MDT0
method 1
AT0
AT1
AT2
AT3
MDT0
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H S
D 3
R H
H M
D S
R T
RT channel
method 2
Communication cycle




Communication cycle is partitioned in Real-Time channel and Non Real-Time channel
Up to 4 telegrams per data direction (max. 6.000 byte)
Master Data Telegrams and Acknowledgment Telegrams are transmitted by the master
NRT channel integrated in separate time slot, no modification of the ETHernet
telegrams necessary
(c) SERCOS International 2009
No. 15
SERCOS III Telegram Structure
S III Header (MST)
Hot plug field
Service channel (SVC)
Real time data (RTD)
S III Header (MST)
 MDT/AT data are protected via FCS and transmitted by the master.
 MST is valid in MDT0...3 and AT0…3.
 MDT




AT



Every slave receives the MDT and take its data.
The MDT is repeated only, not changed by the slave
MST in MDT0 only is used for synchronization purposes.
Slaves insert data in the AT data field
Slaves process cross communication in AT only
Every slave checks the Rx-FCS and determines the Tx-FCS
preamble
SFD
destination source
address address
6 Byte
6 Byte
0x88CD
MST
(S3H)
MDT/AT
data field
FCS
IFG
2 Byte
SERCOS type
(MDT/AT)
phase
CRC
1 Byte
1 Byte
4Byte
checked via CRC
(c) SERCOS International 2009
No. 17
MDT and AT data fields

MDT/AT data field may contain up to 3 fields

Hot-plug (HP)

Service channel (SVC)

Real-time data (RTD)
preamble
SFD
destination source
address address
Hot-plug field
(new slaves)
(c) SERCOS International 2009
0x88CD
MST
(S3H)
Service channel field
of slaves
MDT/AT
data field
FCS
IFG
Real-time data field
of connections
No. 18
Real-time data structure


Real-time data field contains:

Master/Slave data

Cross communication (CC) data
Length of real-time data field : configurable
Service channel field
of slaves
Hot-plug field
(new slaves)
MDT0-3 or
AT0-3
real-time data
slave # 1
M/S connection
data
slave # 1
(c) SERCOS International 2009
real-time data
slave # 2
Real-time data field
of connections
•••••
real-time data
slave # K
Cross
communication
data of slaves
CC data
also possible
slave # 1
No. 19
Initialization
Initialization
Communication phases (CP0 to CP4)
Start
Address
allocation
1
NRT
mode
MDT0-CP0
CP0
Communication
Slave
parameter
identification
setup
CP1
Application
parameter
setup
RTD are don‘t
care
Communication
in operation
CP3
CP2
S-0-0127
S-0-0128
CP4
store and
forward
1 = no MDT0-CP0 within 65 ms
CP = Communication phase
NRTmode = non real-time mode
(c) SERCOS International 2009
No. 21
CP0
MDT / AT structure
preamble
SFD
SERCOS type phase
= MDT0-P/S
=0
destination source
address address
CRC
Comm.
Version
4 Byte
type
MST
(S3H)
MDT/AT
data field
FCS
IFG
36 bytes
padding
1024 bytes
SERCOS type phase
= AT0-P/S
=0
CRC
SEQCNT
2 Byte
AT0-P (primary channel) 
TADR
#1

2 Byte
TADR
#510
2 Byte
TADR
#511
2 Byte
Master set SEQCNT = 0x0001
AT0-S (secondary channel)  Master set SEQCNT = 0x8001
Master set all Topology ADdResses to 0xFFFF
(c) SERCOS International 2009
No. 22
CP0
Address allocation, Slave function
SERCOS type phase
= AT0
=0
CRC
Function of Slave
with TADR #2
SEQCNT
R
+1
SADR is written in
the field of TDAR#2
W
TADR
#1
TADR
#2

TADR
#511
W
SADR
TADR
TADR = Topology address
SADR = SERCOS address, available via switch or parameter
Slave reads and increments the content of SEQCNT in AT0 to determines the Topology address (TADR)
Slave writes the SERCOS address in the corresponding TADR
(c) SERCOS International 2009
No. 23
CP0
Address allocation, Master with ring (examples)
 4 slaves without addressing error
 SERCOS addresses #1, #10, #11 and #0
AT0-P
data field SEQCNT TADR TADR TADR
#3
#2
#0
#1
contents 0x0005 0x0001 0x000A 0x000B
TADR
#4
0x0000
TADR
#5
0xFFFF
TADR
#4
0x00FE
TADR
#5
0xFFFF

TADR
#511
0xFFFF

TADR
#511
0xFFFF
 4 slaves with addressing error
 SERCOS addresses #1, #0, #1 and #254
AT0-P SEQCNT TADR TADR TADR
data field
#3
#2
#0
#1
contents 0x0005 0x0001 0x0000 0x0001
 Diagnostics in the Master
 wrong SERCOS address (0 or >511)
 same SERCOS address (add-on to S II)
 additional SERCOS address
(c) SERCOS International 2009
No. 24
Synchronization generation
MDT0
AT0
H M
D S
R T
H S
D 3
R H
IP telegrams
MDT0
H M
D S
R T
RT channel
IP channel
communication cycle
synchronization signal
(once per cycle)
Synchronization is generated by the MST field of MDT0 only.
(c) SERCOS International 2009
No. 25
Synchronization with MST
SERCOS cycle (tScyc)
AT0 transmission time (t1)
synchronization trigger
Start in
Master
NRT channel (t6, t7)
Synchronization delay time
2,24 µs (28 Byte, constant duration)
propagation delay:
preamble SFD
7+1 Byte
destination source
address address
6 Byte
6 Byte
type
MST
MDT
data field
FCS
2 Byte
IFG
4 Byte
SERCOS type
(MDT0)
phase
CRC
1 Byte
1 Byte
4Byte
checked via CRC
(c) SERCOS International 2009
No. 26
Physical delay times
Slave and cable
 Slave delay (trep): FPGA and netX meas. 600ns
 Cable delay (tcable):
 CAT5e max. 5,56 ns / m (max. 556 ns / 100 m)
 Glass fiber max. 5 ns / m (max. 500 ns / 100 m)
PHYRx PHYTx
220ns
90ns KS8721BL
215ns
60ns DP838481
170ns
50ns
LXT973
600ns with PHY
netX
Micrel
NSC
Cortina
Hilscher
SERCOS III Slave path delay
ca. 170-220 ns
PHYRx RX
TX FCS
170ns 160ns 160ns 0ns
PHYTx Delay
50ns 540ns
PHY Rx
ca. 50-90 ns
PHY Tx
Rx-Fifo
Tx-Fifo
FCS
FCS
generator
(c) SERCOS International 2009
No. 27
Determine the SYNC time with Ring
Ring delay is calculated by the master and transmitted to all slaves
Every slave has a SYNC counter on P1 and P2
Example: 4 slaves with addresses #1, #10, #11 and #254
20
control unit
0
P2
P1
slave
addr. #10
SYNCCNT_P1
SYNCCNT_P2
100
20
P1
20
P1
P2
slave
addr. #1
80
40
15
120
30
P1
P2
slave
addr. #11
50
70
35
P2
slave
addr. #254
15
105
Ring delay = Σtrep + Σtcable + safety margin
(c) SERCOS International 2009
No. 28
Determine the SYNC time
Example with Ring
0
10
20
30
40
50
60
70
80
90 100
110
120
#10
SYNCCNT_P1= 100
SYNCCNT_P2= 20
1. Slave_P1
4. Slave_P2
#1
SYNCCNT_P1= 80
SYNCCNT_P2= 40
2. Slave_P1
3. Slave_P2
#11
SYNCCNT_P1= 50
SYNCCNT_P2= 70
3. Slave_P1
2. Slave_P2
4. Slave_P1
1. Slave_P2
SYNCCNT_P1= 15
#254 SYNCCNT_P2= 105
Ring delay = 120
(c) SERCOS International 2009
SYNC ref time
for all slaves
No. 29
Hot-plugging
Hot-plugging
Hot-plug phases (HP0 to HP2)





Hot-plugging is possible with line only
with ring, a ring break has to initiated first
Hot-plug function active on one channel only (P or S)
Master shall be prepared for the HP slave
Hot-plugging consists of 3 phases (HP0 to HP2)
1
Start
NRT
mode
CP0
MDT0-CP0
1 = no MDT0-CP0 within 65 ms
2 = HP Slave activates Loopback
Master commands FF to last slave
3 = Master switches from HP field to SVC
4 = Master activates timing of CP3/4 (S-0-0127)
5 = Master activates operation mode (S-0-0128)
CP0 = Communication phase 0
NRTmode = non real-time mode
HP = Hot-plugging
OL = Operation level
OM = Operation mode
(c) SERCOS International 2009
MDT0-CP4
HP0
CP4
OM
2
CP3
OL
HP2
HP1
3
5
S-0-0128
4
S-0-0127
No. 31
IP Communication
(NRT-Channel)
IP Communication
General
Master
primary or
secondary channel
P1
S III Telegrams and
IP Telegrams
Slave 1
P1
Line
P2
Slave 2
P2
P1
P2
Slave 3
P2
P1
Collision
Buffer
IP Telegrams only
 Collision Buffer is available in each slave
 PC receives S III telegrams and IP telegrams
 PC transmits IP telegrams only
(c) SERCOS International 2009
No. 33
IP Communication
Ring topology
PC1
Ethernet (Office)
IP
Master
P1
P2
I/O
(c) SERCOS International 2009
No. 34
IP Communication
NRT-Plug with ring topology
Ethernet
P1
P2
NRT-Plug
Function of NRT-plug:
- Only the NRT-channel is processed
- Real-time telegram passes through / are forwarded
Standard Industrial
Ethernet Switch
NRT domain
SERCOS III
(c) SERCOS International 2009
No. 35
IP Communication
Line topology
PC1
Ethernet (Office)
IP
Master
P1
P2
PC3
I/O
PC2
(c) SERCOS International 2009
No. 36
IP Communication
Commisioning without S III communication
IP
I/O
 Download/Upload via NRT-channel in non-real-time mode in line topology
 PC is connected to a unused port
(c) SERCOS International 2009
No. 37
Parameter Model
Device Model
Introduction to IDNs (1)
IDN = Identification Number
SERCOS III
Master Device
SERCOS III Slave Device
FSP IO FSP Drive
…
Generic Device Profile
SERCOS Communication Profile
Communication
Application &
Communication
Functions
Mapped to IDNs
Communication
SERCOS III
(c) SERCOS International 2009
No. 39
Introduction to IDNs (2):
Example of IDNs





S-0-1002 Communication Cycle time (tScyc)
S-0-1003 Allowed MST losses in CP3/CP4
S-0-1035 Error counter Port1 and Port2
S-0-1040 SERCOS address
….
 S-0-0390 Diagnostic number
 S-0-1303 Diagnosis trace
 …
 S-0-0047 Position command value
 S-0-0040 Velocity feedback value
 …
 S-0-1503 Digital Input
 S-0-1504 Analog Output
 …
(c) SERCOS International 2009
SCP
GDP
FSP Drive
FSP I/O
No. 40
Introduction to IDNs (3)
SERCOS III
Master Device
SERCOS III Slave Device
Communication
S-0-0040 S-0-0047
S-0-….
S-0-1503 S-0-1504
S-0-….
FSP Drive
FSP I/O
S-0-0390 S-0-1303
S-0-….
GDP
S-0-1002 S-0-1003
S-0-….
SCP
Communication
S-0-0047
S-0-1503
(c) SERCOS International 2009
No. 41
Introduction of 32-bit IDNs
SERCOS II
SERCOS III
(c) SERCOS International 2009
No. 42
IO Addressing schema
(c) SERCOS International 2009
No. 43
Performance
Communication performance
Cyclic
data
8
12
16
12
32
12
50
32
12
Byte
Byte
Byte
Byte
Byte
Byte
Byte
Byte
Byte
Cycle
time
No. of
slaves (1)
31,25 us
62,5 us
125 us
250 us
250 us
500 us
1 ms
1 ms
1 ms
7
14
26
61
33
122
97
137
251
No. of
slaves (2)
No. of
slaves (3)
No. of
MDT / AT
30
17
94
85
120
220
2
8
21
57
31
120
95
134
245
1/1
1/1
1/1
1/1
1/1
2/2
4/4
4/4
4/4
10 slaves with S II
20 slaves with S II
1) without NRT channel
2) with NRT channel: 1500 bytes = 125 µs
3) with NRT channel: 250 bytes = 20µs
(c) SERCOS International 2009
No. 45
Conclusion
Technical characteristics (1)
Top 5 differentiating advantages
 Communication redundancy (recovery time < 25 µs!)
 Direct cross-communication (without master involvement)
 Controller to Controller (C2C)
 Slave to Slave (CC)
 Standard TCP/IP communication
 without additional hardware
 without running S III Communication
 Hot-plugging of slaves during operation
 SERCOS SoftMaster supports standard Ethernet Controller
when < 1µs determinism is not required.
(c) SERCOS International 2009
No. 47
Technical characteristics (2)
More advantages of SERCOS III
 Diagnosis with standard sniffer-tools (freeware): telegram data recording within the
topology (e.g. Ethereal / Wire shark), SERCOS III Plugin available
 Physical and Logical addressing (up to 511 Slaves)

Physical addressing is used during initialization

Logical addressing is used in operation and parameter setup
 Easy migration from SERCOS II to SERCOS III
 Reduction of bus systems - one bus for all field devices
 Cost reduction with CAT5e Cabling
 Higher transmission rate (~ 6x faster than SERCOS II)
(c) SERCOS International 2009
No. 48
SERCOS III – Ethernet based Real-time Communication
for Motion, Safety and I/O
Thank You for Your Attention
More Questions?
(c) SERCOS International 2009
No. 49