Advanced Embedded Systems Design

Lecture 13 RISC-CISCBAE 5030 - 003

Fall 2004Instructor: Marvin Stone

Biosystems and Agricultural EngineeringOklahoma State University

Goals for Class Today

• Questions over reading / homework• Review CISC vs RISC - Ragu• J1939/ISO 11783 - (Stone)

Essence of ISO 11783an Electronics communications protocol standard

– Allows manufacturers to build electronic components that communicate with each other

• Examples:– Instrument cluster and engine Electronic Control Unit (ECU)– Tractor ECU and Implement ECU– Grain Flow ECU and Virtual Terminal ECU

– Uses multiplexed wiring• ECUs communicate across a shared four wire cable

• Bit serial communications

– Based on CAN protocol• Robert Bosch GmbH protocol for automotive use

Network Structural Model

VTTask ControllerMgt. Computer

Gateway GPS

Hitch

Implement BridgeImplement ECU and

ImplementECU

ImplementECU

Transmission

TractorECU

Engine

Implement Bus

Tractor Bus

Implement Sub-network Bus

CAN based Ag related standards

• ISO 11783 uses pieces of J1939 and DIN 9684.• At the CAN level J1939 and 11783 use the same 29

bit CAN 2.0b

ISO 11783

SAE J1939DIN 9684(LBS)

CAN 2.0a (11 bit)

CAN 2.0b (29 bit)

Mention NMEA 2000

Standards Bodies - Relationships

ISO

ANSI

Agricultural ElectronicsISO/TC23/SC19

Mobile AgriculturalCommunication Network

ISO/TC23/SC19/WG1

ANSI Designate

AMI

Technical Advisory GroupISO/TC23/SC19/WG1 TAG

(US Policy RegardingWG1)

SAE

ASAE

SAE Truck and BusElectronics Control

and CommunicationsSub-committee

Application Layer TaskForce

Data Link Layer Task Force

Diagnostics Task Force

Con Ag Task Force

About 10 Addnl. TaskForces

Instrumentation andControl (IET 353)

Mobile CommunicationsNetwork Sub-Committee

(IET 353/1)

Off-Road ElectronicsCommittee

International

National

North American ISOBUSImplementation Task

Force (NAIITF)

ISO 11783 SAE J1939

ISO 11783 Characteristics

• Attempts to• Standardize communications to the extent that ECUs built by

different manufacturers can communicate.

• Allows• Ag Implement applications (precision farming apps.)

• Powertrain/Braking/Lighting/Instrument Panel apps.

• Standardized and proprietary information exchange

• Control loops across net (10 ms repetition)

• Data rate 5.6k bytes/sec. @ 30% load, bursts to 16k bytes/sec.

• 30 nodes per subnet, 254 nodes per system

Hardware review

• How far, how fast, how many nodes• Types of nodes (if there are any). Etc.• How long of a cable can we use?

– Is this length a total length or from piece to piece?– Is there such a thing as a line driver, or booster?

• What is required in the way of line terminations?

J1939 / ISO 11783 Physical LayersMaximum number of ECU's

– 30 (per segment)• ISO 11783 Media

– Twisted Quad un-shielded• 75 nominal impedance• Two data lines (CAN_H, CAN_L)• Two termination supply lines

• J1939-11 Media– Shielded twisted pair

• 120 nominal impedance• Two data lines (CAN_H, CAN_L)• One shield

• Signal– Compatable with ISO 11898 drivers (eg. Phillips 80C250)

• Termination– J1939 – 120 passive– ISO 11783 – Active balanced current design

Cableing

Cable Cross-section

CAN_L

CAN_HTBC_PWR

TBC_RTN

Jacket

CAN_L

CAN_H

FillerShield

Filler

J1939-11 ISO-11783

ISO 11783 Physical Layer

• Bus Fault Tolerance:– Continued communications (emissions failure?)

• CAN_H shorted to Vbat or Ground or interrupted

• CAN-L shorted to Vbat or Ground or interrupted

– Communications Failure• CAN_H Shorted to CAN_L

• Terminator power interrupted

• ECU Conformance Testing– Test specifications included

Bus Length and Geometry

• Maximum Segment Length (L): 40 m• Maximum Drop Length (S): 1.0 m• Minimum Node Separation (d): 0.1 m

ECU1

ECU2

ECUn-1

ECUn

L

ECU_PW R

T erm inatingBias

C ircuit

4

4

2

4

2

4

T erm inatingBias

C ircuit

d

S

Distance 'd ' is recommended to be random, but not less than 0.1 m

ECU_G ND

ISO 11783 Connectors

Implem ent Bus

OptionalECU StubConnector

DiagnosticConnector

Tractor Bus

BusIn-CabConnector

Terminating BiasCircuit w / Netw orkPow er Connection

BusBreakaw ayConnector

E C U 1

11783P art 2

E C U 2

11783P art 2

E C U x

11783P art 2

E C U z

11783P art 2E C U y

S A EJ1939 /11

Tracto rE C U

Tractor Implem ent 1

E C U n

11783P art 2

E C Un-1

11783P art 2

E C Un-2

11783P art 2

Implem ent 2

B atte ry

OptionalAutom aticTerminatingBias Circuit

TerminatingBias Circuit

Standard Connectors

Optional Standard Connectors

Proprietary Connectors

Autom atic

BusBreakaw ayConnector

Autom atic

Automatic Terminating Bias Connector

• Disconnection does not disrupt communications• Provides Power and data

ISO 11783/J1939 Architecture

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Physical Layer

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Physical Layer

CAN CAN

Ne

two

rk M

an

ag

em

en

tNe

two

rk M

an

ag

em

en

t

Data Link LayerData Link Layer

ECU 1 ECU 2

J1939 / ISO 11783 Data Link Layer - General

– Based on CAN 2.0b 29 bit identifiers• Defines the identifier meaning

• Physical Addressing ( 256 addresses)

• Independent priority field

• Data content identifier independent of sender

• Two message structures– Type 1 - Destination Specific - both source and destination– Type 2 - Extended - Only source address

– Defines requests and acknowledgement– Defines proprietary message structure– Includes a Transport Protocol with two modes

» Managed Connection» BAM

Message Capabilities

• Two identifier types (PDUs)– ECU to ECU– ECU to All

P P P R GPDU 1

PDU 2 P P P R G

Reserved First 8 BitsBetween 240 and 255

Source AddressDestination Addr

Page Bit

TYPE

Priority

Parameter Group

Source Address-- PDU Format -- Group Extension -

Parameter Group

P P P

P P P

Destination Addr.

Source Address

Source Address

PDU Specific

Parameter Group IdentifiesData

Group ExtensionR D

R D PDU Specific

Source AddressIdentifiesSender

PDU2

PDU1

Priority

8670 Parameter Groups can be defined480 PDU1, 8190 PDU2

Identifier Structure

PGN - Parameter Group Number

Parameter Group Number (PGN)

P P P

Destination Address orGroup Extension

Source AddressR PDU Specific

PDU Specific (PS)R DP

If (PS > 239)LS Byte = PF

Else LS Byte = 0

LS Byte

DP PDU Format (PF)

0 0 0 0 0 0

Byte 2 LS ByteMS Byte

Parameter Group Number (PGN) arranged fortransmission as a parameter

Byte 2LS Byte

Identifier

PGN

PGN

PGN ArrangedMS Byte

Message Capabilities

P P PPDU1

One to ManySOURCE

DESTINATION

OR

P P PPDU2

--------- 255 ---------

- Source Address --

- Source Address --

-- Parameter Group --

-- Parameter Group --

Global

Message Capabilities

PDU1

One to One

SOURCE DESTINATION

-- Parameter Group -- Source AddressDestination Addr.PP P

Message Capabilities

P P P

AcknowledgementSOURCE DESTINATION

SEND

ACKNOWLEDGE

P P P

Command

SourceDestination

AcknowledgeACK / NACK ECU AECU B

Control Byte Reserved

1 2-5

Acknowledged orRequested PGN

Data

OrNormal Broadcast

0 = Positive Acknowledgement1 = Negative Acknowledgement2 = Access Denied3 = Cannot Respond Now No Acknowledge on Global Requests

----------- 59392 -------------

ECU A ECU B

PGN

6-8

0 1 1

PDU1

Requests

SOURCE

Destination Address

SOURCE

Source Address -

OR

DESTINATIONS

PDU1

Global

Specific

1

DataPGN lsb PGN

2 3

------- 255 ----------

Global

Request

Request

PGN msb

----------- 59904 -----------

----------- 59904 ----------- Source Address -

1

DataPGN lsb PGN

2 3

PGN msb

0 1 1

Message Capabilities

Reply’s to Requests

PDUFormat

DataLength

RequestType

Response TP Used

1 < 8 bytes DA Specific DA Specific NA1 < 8 bytes DA Global DA Global NA1 > 8 bytes DA Specific DA Specific RTS/CTS1 > 8 bytes DA Global DA Global BAM2 < 8 bytes DA Specific PDU2 Global NA2 < 8 bytes DA Global PDU2 Global NA2 > 8 bytes DA Specific DA Specific RTS/CTS2 > 8 bytes DA Global DA Global BAM

P P P

---------- 239 ----------

PDU1

Proprietary

SOURCE

Destination Address

SOURCE

Source Address

OR

P P P

----------255------------

PDU2

DESTINATIONS

--- user defined ---- Source Address

0

0

0

0

Message Capabilities

1 0 0

TP.CM_RTSRequest to Send

Source Address -Destination Address

Multi-PacketMessages

SOURCE

DESTINATION

Connection Mode

Connection Mode - START and DATA PACKETS

10

TP Control No. of Segments

161 byte

Data

1 byte 2 bytesNo. of Bytes Message PGN

3 bytes

1 0 0

TP.CM_CTSClear to Send

10

TP Control Next Segment

171 byte

Data

1 byteSegments to

Send1 byte

TP.DTPacket Data

Packetized Data7 bytes

Reserved1 byte

SENDERRECEIVER

SENDER RECEIVER

Sequence No.1 byte

TP Conn. Mgt.

--------- 236 -----------

Source Address -Destination Address--------- 236 -----------

Message PGN3 bytes

Reserved2 byte

1 0 010

SENDER RECEIVER TP Data Xfer.

Source Address -Destination Address--------- 235 --------

Data

TP Conn. Mgt.

TP.EndOf MesgACKACKNOWLEDGE

TP.ConnAbortAbort Connection

Multi-PacketMessages

Connection Mode

Connection Mode - ACKNOWLEDGE or ABORT

SOURCE

DESTINATION

1 0 0 Source Address -Destination Address10

SENDERRECEIVER TP Conn. Mgt.

--------- 236 -----------

1 0 0 Source Address -Destination Address10

SENDERRECEIVER TP Conn. Mgt.

--------- 236 -----------

TP Control No. of Segments

191 byte

Data

1 byte 2 bytesNo. of Bytes Message PGN

3 bytesReserved

1 byte

TP Control

255

Data

1 byteMessage PGN

3 bytesReserved

4 bytes

Message Capabilities

200 ms between data packets!

TP.CM_BAMBroadcastRequest to Send

Multi-PacketMessages

SOURCE

DESTINATIONBroadcast Mode

1 0 0 Source Address -Destination Address10

SENDERRECEIVER TP Conn. Mgt.

--------- 236 -----------

TP Control No. of Segments

321 byte

Data

1 byte 2 bytesNo. of Bytes Message PGN

3 bytesReserved

1 byte

TP.DTPacket Data

Packetized Data7 bytesSequence No.1 byte

1 0 010

SENDER RECEIVER TP Data Xfer.

Source Address -Destination Address--------- 235 -----------

Data

Message Capabilities

Design Recommendations

• REQUEST SCHEDULING– The scheduling of a request should be canceled if

information requested is received prior to request being sent. Parameter Groups should not be requested if they are recommended to be broadcast.

Design Recommendations

• DEVICE RESPONSE TIME AND TIME-OUT DEFAULTS– All devices, when required to provide a response, must do

so within 0.20 s. All devices expecting a response must wait at least 1.25 s before giving up or retrying.

Design Recommendations

• REQUIRED RESPONSES– A response is required for a global request from all

devices that have the requested PG, even the requester. Acknowledgments are not allowed for global requests. There is no restriction on minimum response time!

Design Recommendations

• CTS NUMBER OF PACKET RECOMMENDATION – During normal vehicle operation it is recommended that

the maximum number of packets that can be sent per CTS be set to 16.

Assignment

• Continue:– Demonstrate sending and receiving a CAN message– Prepare Portfolio

• Organize with regard to milestones in course– Review each milestone– Assess your accomplishment of each milestone

• Include resources– Lecture materials– Outside reading – assigned and other

• Commented listings