APPLICATION NOTE
ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
by L. PERIER / A. COEN
Replacing a classical harness with a multiplexing (mux) network makes cars more competitive as it increases their flexibility and simplifies the wiring. CAN is the leading protocol for car mux systems thanks to its large speed spectrum and noise immunity. But each application has specific constraints in terms of protocol, cost and performance. So a single node architecture does not fit all the needs. This article compares first of all, the major car mux protocols: CAN, J1850 and SCI/UART. The se c o n d part describes optimized nodes including microcontrollers (ST725x, ST92F120, ST10 F167) with embedded FLASH/ROM and physical line interfaces (U435). Then it presents roadmaps for MCU cores, embedded FLASH memories and super-integrations.
1 MULTIPLEXING FOR SMARTER CARS
1.1 THE CHALLENGES Automotive is a tough business: the industry has heavy over-capacities (i.e. 20 to 30% in Euro pe), cities are overcrowded (i.e. 2/3 of the populations is expected to live in cities in 2025 versus 1/3 now) and governments apply restrictive regulations for safety and environment (i.e. Clean Air Act or airbag deployment act in the USA). New cars must be cheaper, cleaner, safer, smaller.... and so smarter. One of the weak points is the harness. A typical harness represents 35 kg, 1 mile of wiring and 300 connectors costing over 1k US$. In addition, systems require distributed intelligence with a lot of communication. A web inside the car enables flexible platforms to be built, sharing more information with less wires, connectors and sensors. In addition, only multiplexing can fit requirements with regard to safety and diagnostics. But Automotive has harsh constraints: cost, environment and reliability which lead to specific protocols and implementations. Now vehicle multiplexing is a reality in high-end cars with up to 30 nodes in the network (Cf. figure 1) and is spreading rapidly to lower-end models presently in design.
AN1086/0199
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
Figure 1. Example of a car CAN network
ENTERTAINMENT
AUDIO VIDEO WIRELESS Low speed CAN 2.0B passive < 125 kbps Door Module Radio Car-Phone Door Module Audio Power Navigation Trunk Module TV-Module Video-Box Air Cond Pass.-Seat Driver-Seat Gearbox Door Module EMS
BODY
COCKPIT - DOOR CENTRAL - REMOTE
POWER-TRAIN
TRACTION STABILITY
Door Module
Dashboard CAN Gateway
E-Star ter
DIAGNOSIS
ISO9141 10kbps Traction
Very high speed ie D2B-Bus up to 100M bps
Doom-Control
Backseat Central Airbag Light C. Rear
ABS+ASC High speed CAN2.0B active 125 kbps to 1Mbps
Contr.Pannel.
A CAR INTRANET
Light C. F ront
Immobiliser
Park-Tronic
VR02136A
1.2 THE SOLUTIONS 1.2.1 The Supply: Available but Noisy The supply is a two-wire network available "for free" in all cars. But is difficult to use because of the disturbances induced by the different loads (i.e. 12 V Nominal = 40 V peak during loaddump and up to 100V during short transients). Neverth eless it is used in some applications (i.e. smart sensors) with current modulation at relatively low speed (around 100 kHz). Furthermore, studies are ongoing to move to a double sup ply architecture (42Vdc/75Vpeak for power loads and 14Vdc/33V peak for low power) to decrease the current and the losses in the power loads. Such an approach better uses semicon du cto r technologies (i.e. BCD3S 1.0u for 42V and BCD5/6 0.5/0.35u for 12V) in developing low cost super-integrated nodes.
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1.2.2 The Car Web Protocols A Darwinian Selection Process. Co nsid erin g the applications' requirements, a dedicated network is obviously needed. The ideal network should use an open system, reliable if noisy, with low CPU usage, short transmission times...and all that for free. It should support different data link classes (Cf. table 1) and safe diagnosis from an external system. Table 1. Messages Speed Classes
Class A B C Speed kbps <10 10 to 125 > 125 Application electric diagnostic display, sensor real time message latency 100 ms 20 ms 5 ms protocol CAN J1850 (GM-Chrysler) SCI/UART CAN J1850 (Ford) CAN
However, the ideal network does not exist and 3 main protocols are in use: CAN, J1850 and SCI/UART. Table 3 summarizes their main characteristics. CAN is the only protocol really designed to cover a large speed spectrum (up to 1Mbps) in n o isy environments (thanks to powerful error management, multimaster architecture and physical lines interface definitions). It is now used extensively in European automotive and industrial markets. An open operating system is available (Osek/VDX) to describe the application layer (long messages, interrupt management,...). In addition, conformance tests (i.e. Dassault, IVS/C&S) are now available to validate that the microcontrollers operate in compliance to the CAN standard. Two major configurations are in use: "CAN 2.0B Active" for power train (29-bit identifier supported) and "CAN 2.0B Passive" for body and entertainment (11-bit identifier supported, 29-bit identifier tolerated). J1850 and SCI/UART are more restricted to specific areas: Diagnostics and body in USA for J1 850; Diagnostics in Europe and simple "node to node" customized networks independent from the main network for SCI/UART.
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2 SYSTEM SOLUTIONS FOR MUX NODES
Due to the diversity of the applications, a single node architecture can not fit all the needs. Thanks to a strong partnership with major actors of the automotive industry and to a long experie nce in power, memories and micros, ST has developed a set of cost-effective components optimized for these applications. 2.1 THE CORE FOR THE NODE A typical MUX node (figure 2) contains a microcontroller (MCU), FLASH or ROM program me mo ry, EEPROM data memory and power devices for physical line interface and supply m anagem ent. Figure 2. Typical node block diagram
Vbat VREG Program Memory FLASH ROM
Data Memory EEPROM
In
Sensor Signals analog, digital
Watchdog Supervision
Microcontroller
CANH CANL
CAN Transceiver
TX RX
CAN Control
Out
Actuators Signals
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
MCU core requirement can move for the same application, i.e. body controller from 8-bit to 16bit, depending on the application complexity (figure 3). Figure 3. Microcore versus application
Power Train 32 Bit Engine Control Transmission ABS/ASR Steering Suspension Sensors Multimedia GPS Digital Radio Analog Radio Cluster LCD CD Display Vehicule Control Body/Chassis Entertainment
16 Bit
8 Bit
Watchdog
Air Cond. Computer Wiper Access Power Lighting Door Control Keyless
Airbag
8/4 Bit Analog
ST provides a complete range of MCU cores to cover this variety of needs (table 2). The products derived from these cores use a design flow fully compliant with automotive requirements: This maximizes the test coverage through VHDL description, Scan chain, JTAG and specific test flows (i.e. Iddq); Electro Magnetic Compatibility (EMC) is taken into account in the design th a nks to a macrocell library optimized to minimize emission and ensure high robustness; Mea su reme nt tools are dedicated to investigate the practical EMC results; Product families are derived from a FLASH or EPROM master using the same basic technologies and CAD flow.
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Table 2. Table 2: ST MCU cores: 8 and 16-bit
FEATURES Architecture ST6 Serial 8bit Accumulator 8k 8MHz 6.5s 42 SW SW No No 5 vectors 3V <1 ST7 Parallel 8bit Accumulator 64k 16MHz 250ns 63 HW (1,375s) SW No Yes 16 vectors 1.8V 1 ST9 Parallel 8/16bit Register File 4M 24MHz 250ns 87 HW (920ns) HW (1,08s) Yes Yes 128 vectors 1.8V 2.5 ST10 Parallel 16bit Register file 16M 50MHz 160ns 84 H/W (400ns) H/W (800ns) Yes Yes 56 vectors 1.8V 6.5 (incl. 512B DPRAM)
VR02136J
Direct Address Space Exter nal clock speed Instruction speed (load/move) Nb of instructions Multiply Divide "C" instructions DMA Interrupt Low voltage Relative core area (core + itc + dma + reg. file)
(*) ST6 / ST7 figures are given for 0.8 technology, ST9 / ST10 for 0.5 . (except for Relative core area where the four cores are compared in the same tec hnology)
Two microcontroller families have been designed to cover the CAN application: The ST725xx fo r CAN passive "low speed" applications (mainly body) and the ST10F16x for CAN active "high speed" systems (mainly power train). All these devices include also an SCI/UART to provide diagnostic capability. For J1850, the ST92F120 family has been designed. It supports the Chrysler/Delco protocol.
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2.2 BODY CAN NODE: SOLUTIONS FOR DOOR MUX Door multiplexing shows different possible implementations, from centralized to decentralized architecture. The following drawings present block diagrams of possible implementations from the simplest one to the most advanced Mechatronic approach (figure 4) Figure 4. Possible Door System partitioning
M irror Key b . Key b .
Central A p p r o a c h . N o electronics inside door
M irror Key b . Actuator d r i ve r s
Local Approach . All d r i ve r s o n 1 PC- board
W inlift
Latch
W inlift
Latch
Actator d r i ve r s
CAN-Bus
CAN-Bus Local Approach . A l l dr i v e r s a t t a c h e d t o winlift actuator Mechatronic Approach . Each actuator use s e p a r a t e a t t a c h e d dr i v e r
M irror Key b . CAN-Bus
M irror Key b . D r i ve r
W inlift
Latch
W inlift D r i ve r
Latch D r i ve r
Actator d r i ve r s
CAN-Bus
VR02136B
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
The local approaches (figure 5) are built around the ST725xx microcontroller. This family include s several subset ROM versions derived from the following master: 8-b it ST7 core, 60kbyte program, 2kbyte RAM, SPI, SCI/UART, CAN 2.0B passive, 2x16-bit Timers, 8-bit ADC, low power modes in TQFP64 package. The other components, mainly power devices, are developed in BCD technology. The Mirrors could be also controlled independently from the CAN network through an SCI/ UA RT communication, if judged necessary for safety reasons. Figure 5. A door controller on one PC-board
CAN Bus Driven
Vbatt U 435 Vreg
ADC L 9997
M M
Mirror motors
Reset Wtchd . W ake up W . up TX Body CAN CAN RX VND10BSP
Microcontroller ST725xx CAN
L 9997
Defroster Side lamp
M
Door Latch VN 770P Relay + discrets
Window lift
HallSensor
M
VR02136C
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The Mechatronic power latch presented in figure 6 embeds in the same SuperSmartPower (SSP) chip an 8-bit microcore (ST6) with a power stage to supply the circuit and drive the latch motor. This L9942 was developed in BCD3 (1.2um) technology. Later versions are in design using BCD5 (0.6um) and embed logic and memory features similar to the ST725xx. Such an approach is especially advantageous in applications whee size is very critical. Figure 6. Mechatronic Power Latch L9942
Vs Main 5V Regulator Run PA0 PA3 4KB ROM 8-bit Timer Digital Watchdog CAN Bus CAN Controller CAN Bus driver RC Osc. CPU Bus ST6 CORE Port A 128B RAM Bridge Logic Bridge Driver PVs
Vbatt
Vbatt
Regulator + Reset
Charge Pump
M
Volt.Monitoring Overtemperature + Overload Prot.
Latch Motor
XTL
Contact Monitoring
GND Latch contacts
PGND
VR02136D
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
2.3 LIMITS OF INTEGRATION: A LIGHT CENTER The following example (figure 7) presents an example of a highly integrated lighting control center using the same master ST725xx microcontroller and dedicated power devices. Due to the power requirements, an integration with SSP is not considered. An application requiring very high voltage capability (i.e. up to 400V in Xenon Gas discharge headlight) would have a similar partitioning. Figure 7. Automotive light center
U435 KL 30 Volt. Reg Reset WD Data Inte. f r CAN CAN Tr ns a. 5V Vdd Microcontroller ST 72511 CAN Reset WD Data TX RX
VN 460
G
V N 450
1 2 3
21W
60W
A
21W
60W
5W
B
55W
W akeup
H
V N 450
1 2 3
21W
C
21W
55W
5W
D
55W
SM
V N 450
Headlight leelling v L9935 5V SB
I
SPI Buzzer
1 2 3
21W
E
21W
55W
5W
F
25W
Buzzer
KL15
Resistor coded ts h wi c
V N 450
2 3
21W 5W
V N 450
J
ADC Inputs
1
21W
1
K
20W
2
5W
Dimmer
3
5W
fi
VR02136E
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
2.4 POWER TRAIN CAN NODE WITH 16-BIT MICROCONTROLLER The following example (figure 8) uses an ST10 16-bit microcontroller, a dedicated high speed CAN line interface L9615 and several other power ICs. The ST10F167 includes 128kbyte FL ASH (or ROM), 4kbyte RAM, SCI/UART, SPI, CAN 2.0B active, 2x16-bit Timer Blocks, 8 channel CAPCOM. It is housed in PQFP144. Using the ST10 instead of the ST7, the processing speed is more than doubled and a CAN Active protocol can be managed. So this configuration is adapted to applications requiring fast communication speed and heavy calculation. Figure 8. Automatic Transmission Unit
V15 L 9615
CAN Link CAN Driver
L 4925
Voltage Regul..
Various Loads
L 9822E
Octal Low Side Driver SPI
5V SPI
ISO Link
L 9637
ISO 9141 Interface
Valve
VND10BSP
Dual HSD 100mOhm Proportional Valve
Micro Controller ST10F167 CAN + Flash Memory
PWM
SPI
L 9790
Sensor Interface
Contact Monitor Input's (max 8)
VN06SP
HSD 180 mOhm
Analog Sensor Input's
Filter
VR02136F
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
2.5 A BODY CONTROLLER WITH J1850 The ST92F120 microcontrollers family is used for body J1850 applications (figure 9). This family includes several subset FLASH versions derived from the following FLASH master: 8/16-bit ST9 core with DMA capability, 128kbyte FLASH, 2kbyte RAM, 1xSPI, 2xSCI/UART, J1 850 Chrysler/Delco, 1xI2C, 6x16-bit Timers, 16 channels 8-bit ADC, low power modes in TQFP8 0/100 package. An EEPROM of 1kbyte is embedded for safety data storage. La te r versions of the ST725xx with J1850 cell are presently in discussion for applications where the ST9 core features are oversized. Figure 9. Body controller with J1850
Indicator Lamps Relay Bank
. . . . . . Dar Dar Dar Dar Dar Dar l l l l l l
. . . Dar Dar Dar l l l
. . . Dar Dar Dar l l l
D . ar l
ST92F120 Microcontroller
VoltageRegulator
Reset Ck
J1850 Phys . Line
Analog /Digital I/Os
VBatt
Speed
VR02136G
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
2.6 SUPER INTEGRATION From Super Smart Power to Distributed Multimedia The race for integration is not finished. For low and medium communication speeds (up to 1Mbps) new solutions based on Super Smart Power enable node size reduction by integrating to g e th e r the physical line interface, the supply and the logic/microcontroller. Products in 0.6um lithography are now in design and the technologies for 0.5um and lower are in developm ent. With these thin lithographies similar to the one uses for standard MCUs, logic and memory features similar to the ST725xx can be embedded (figure 10). Figure 10. Embedding capability of a SSP ST7 device
V Batt
Voltage Regulator
Reset + Watchdog
ST7 Controller Core + Memory
Relay + Gate Drive and ContactMonitoring
M
CAN Controller Hall Sensor Interface Low Speed CAN Transceiver Hall Supply Mosfets: Ron. 6mOhm 30V (25C)
VR02136H
Hall Sensor
CAN
FLASH embedded memory is also a major requirement in automotive to ensure programming capability at the production line and to reprogram the micro during the lifetime of the car. ST10 FLAS H microcontrollers are in full production in 0.5um lithography and samples in 0.35um are availa ble (figure 11). This FLASH process is derived in the 3 versions: a "Full FLASH" enabling above 100k cycles of programming (i.e. for Engine Management control), a "Few Times Prog rammable" version using a slightly simplified and cheaper process variation (i.e. for body applications) and an upgraded version to embed EEPROM emulation capability (i.e. for safety sensitive applications).
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ST7/ST10/U435 CAN-do SOLUTIONS FOR CAR MULTIPLEXING
Figure 11. Embedded FLASH roadmap
0.25 m
ROM
FLASHs V
0.35 m
ROM
FLASHs V
FLASHs V+E3
0.5 m
ROM
F L A S H DV
FLASHs V+E3
0.6 m
ROM
EEPROM
BCD 40V
1998
1999
2000
VR02136I
EE: EEPROM E3: EEPROM/Flash Emulated FTP: Few Times Programmable DV: Double Voltage SV: Single Voltage
New applications such as Distributed Multimedia Systems require even higher communication speed and so faster microcontroller cores. To support such applications, system-on-chip solution s are now in design. They embed different 16 and 32-bit cores from ST20 (25/100 MIPS), ST30 (50/150 MIPS), ST40 (200/400 MIPS) and ST50 (64-bit cpu).
CONCLUSION
Networking is a major trend in our daily life and in system optimisation. Cost effective solutions fully compliant with automotive constraints are now available, based mainly on the CAN protocol . Th ey are built around high voltage devices with 8 and 16-bit microcontrollers. ST725xx or ST9 2F1 20 (FLASH) are used now for low speed body or radio applications and ST10F167 (FLASH) for high speed CAN power train or audio systems. In partnership with major players of the automotive industry, the next step towards system-onchip is in design with additional FLASH-Micros, Super Smart Power and 32/64-bit micro circuits.
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Table 3. Main characteristics of the most used car mux protocols
Peripheral Class SCI/UART A Open Asynchronous Few nodes Masterslave Error detection: checksum J1850 A-B Open Asynchronous Multimaster Bus access: bit arbitration Error detection: CRC Priority on highest header CAN A-B-C
Architecture
Protocol
SCI/UART NRZ (3) Speed Data: 9.6/10.4kbps Speed Address: 5 bps Data: 7bit Frame: 10 bit
Software (Typical)
Diagnosis ISO9141: 2 pins Data: K pin (Rx/Tx) Physical Layer Address: L pin (Rx) Levels: Referred to Vbatt
Datalink Physical Standards
In car MUX: No standard Diagnosis: ISO9141 (Europe) OBD2 (America)
Application None Open protocols In car MUX: nodes isolated from main web for safety (i.e. mirrors) or speed (i.e wiper) purpose. Diagnosis: Std in Europe Industry: used extensively
Running applications
Open Asynchronous Multimaster Error Management Bus access by bit arbitration Priority to dominant bit (0) CSMA/CA2 NRZ 3 Toggling after 5 success bit CSMA/CR1 Speed up to 1Mbps Ford: PWM 41.6kbps Data: 0/8 byte Chrysler/GM: VPM 10.4kbps Frame standard: 0/64 + 47 bit Data: 0/12 byte (up to 2048 addresses)4 Frame: 6 bit Frame extend: 0/64 + 67 bit (500M addresses)4 5 error messages5 Basic configuration: Basic configuration: 4k ROM-64 RAM 2kROM-64RAM Full configuration: All by H/W 2 wires (1 in failure mode/LowFord: 2 wires speed) Referred to 6.25V differential Levels referred to 5V (and Vbatt in Xler/GM: 1 wire Standby_low speed) Referred to 20V max differential Max nodes number: Max nodes number: 32 30 (high speed), 20 (low speed) Max distances: 40m Max distances: 40m @ 1Mbps, 500m @ 125kbps. In car MUX Europe: In car MUX: ISO11898 (>125 kbps, transceiver) SAE J1850 ISO11519 (<125 kbps, transceiver) SAE J2178 In car MUX America : ISO 14230-4 SAE J2284 (high speed/2 wires) Diagnosis: OBD2 SAE J2411 (low speed/1 wire) J1979 SAE J1939/ISO11783 J2190 (truck,< 250kbps) Diagnosis: ISO15765, ISO11898 Real time O/S: OSEK/VDX Industry: standard frame only: None Devicenet (AllenBradley) SDS (Honeywell) CANOpen (CIA) In car MUX (America): In car MUX (Europe): average 3 to 5 nodes average 3 to 5 nodes, up to 36 up to 36 nodes nodes around 20M nodes in 1998 Diagnosis (America) Industry: Devicenet and SDS Industry: none (USA), CANOpen (Europe)
Notes:
1 2 3 4
CarrierSense, Multiple Access, Collision resolution CarrierSense, Multiple Access, Collision avoidance NonReturn to Zero Standard: 11bit, Extended: 29 bit A version: std frame only, error with extended frames B passive: std frame messages, no error if extended frames B active version: std and extended frame messages 5 Error messages in 5 cases: bit, bit stuff, message frame, message CRC, message acknowledge errors.
CSMA/CR: CSMA/CA: NRZ: CAN frames identifier:
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