SAE J1962—Diagnostic Connector
SAE J1850—Class B Data Communications Network Interface
SAE J1939—Truck and Bus Control and Communications Network (Multiple Parts Apply)
SAE J2610—DaimlerChrysler Information Report for Serial Data Communication Interface (SCI)
ISO 7637-1:1990—Road vehicles—Electrical disturbance by conduction and coupling—Part 1: Passenger cars and light commercial vehicles with nominal 12 V supply voltage
ISO 9141:1989—Road vehicles—Diagnostic systems—Requirements for interchange of digital information
ISO 9141-2:1994—Road vehicles—Diagnostic systems—CARB requirements for interchange of digital information
ISO 11898:1993—Road vehicles—Interchange of digital information—Controller area network (CAN) for high speed communication
ISO 14230-4:2000—Road vehicles—Diagnostic systems—Keyword protocol 2000—Part 4: Requirements for emission-related systems
ISO/FDIS 15765-2—Road vehicles—Diagnostics on controller area networks (CAN)—Network layer services
ISO/FDIS 15765-4—Road vehicles—Diagnostics on controller area networks (CAN)—Requirements for emission-related systems
Communication Protocols
The following communication protocols shall be supported:
6.5.1 ISO 9141
The following specifications clarify and, if in conflict with ISO 9141, override any related specifications in ISO 9141:
a. The maximum sink current to be supported by the interface is 100 mA.
b. The range for all tests performed relative to ISO 7637-1 is –1.0 to +40.0 V.
c. The default bus idle period before the interface shall transmit an address, shall be 300 ms.
d. Support following baud rate with ±0.5% tolerance: 10400.
e. Support following baud rate with ±1% tolerance: 10000.
f. Support following baud rates with ±2% tolerance: 4800, 9600, 9615, 9800, 10870, 11905, 12500, 13158, 13889, 14706, 15625, and 19200.
g. Support other baud rates if the interface is capable of supporting the requested value within ±2%.
h. The baud rate shall be set by the application, not determined by the SAE J2534 interface. The interface is not required to support baud rate detection based on the synchronization byte.
i. Support odd and even parity in addition to the default of no parity, with seven or eight data bits. Always one start bit and one stop bit.
j. Support for timer values that are less than or greater than those specified in ISO 9141 (see Figure 30 in Section 7.3.2).
k. Support ability to disable automatic ISO 9141-2 / ISO 14230 checksum verification by the interface to allow vehicle manufacturer specific error detection.
l. If the ISO 9141 checksum is verified by the interface, and the checksum is incorrect, the message will be discarded.
m. Support both ISO 9141 5-baud initialization and ISO 14230 fast initialization.
n. Interface shall not adjust timer parameters based on keyword values.
6.5.2 ISO 14230-4 (KWP2000)
The ISO 14230 protocol has the same specifications as the ISO 9141 protocol as outlined in the previous section.
In addition, the following specifications clarify and, if in conflict with ISO 14230, override any related specifications in ISO 14230:
a. The pass-thru interface will not automatically handle tester present messages. The application needs to handle tester present messages when required.
b. The pass-thru interface will not perform any special handling for the $78 response code.
Any message received with a $78 response code will be passed from the interface to the application.
The application is required to handle any special timing requirements based on receipt of this response code, including stopping any periodic messages.
6.5.3 SAE J1850 41.6 KBPS PWM (PULSE WIDTH MODULATION)
The following additional features of SAE J1850 must be supported by the pass-thru device:
a. Capable of 41.6 kbps and high speed mode of 83.3 kbps.
b. Recommend Ford approved SAE J1850PWM (SCP) physical layer
6.5.4 SAE J1850 10.4 KBPS VPW (VARIABLE PULSE WIDTH)
The following additional features of SAE J1850 must be supported by the pass-thru device:
a. Capable of 10.4 kbps and high speed mode of 41.6 kbps
b. 4128 byte block transfer
c. Return to normal speed after a break indication
6.5.5 CAN
The following features of ISO 11898 (CAN) must be supported by the pass-thru device:
a. 125, 250, and 500 kbps
b. 11 and 29 bit identifiers
c. Support for 80% ± 2% and 68.5% ± 2% bit sample point
d. Allow raw CAN messages. This protocol can be used to handle any custom CAN messaging protocol, including custom flow control mechanisms.
6.5.6 ISO 15765-4 (CAN)
The following features of ISO 15765-4 must be supported by the pass-thru device:
a. 125, 250, and 500 kbps
b. 11 and 29 bit identifiers
c. Support for 80% ± 2% bit sample point
d. To maintain acceptable programming times, the transport layer flow control function, as defined in ISO 15765-2, must be incorporated in the pass-thru device (see Appendix A).
If the application does not use the ISO 15765-2 transport layer flow control functionality, the CAN protocol will allow for any custom transport layer.
e. Receive a multi-frame message with an ISO15765_BS of 0 and an ISO15765_STMIN of 0, as defined in ISO 15765-2.
f. No single frame or multi-frame messages can be received without matching a flow control filter.
No multi-frame messages can be transmitted without matching a flow control filter.
g. Periodic messages will not be suspended during transmission or reception of a multi-frame segmented message.
6.5.7 SAE J2610 DAIMLERCHRYSLER SCI
Reference the SAE J2610 Information Report for a description of the SCI protocol.
When in the half-duplex mode (when SCI_MODE of TxFlags is set to {1} Half-Duplex), every data byte sent is expected to be "echoed" by the controller.
The next data byte shall not be sent until the echo byte has been received and verified.
If the echoed byte received doesn't match the transmitted byte, or if after a period of T1 no response was received, the transmission will be terminated.
Matching echoed bytes will not be placed in the receive message queue.
6.7 Programmable Power Supply
The interface shall be capable of supplying between 5 and 20 volts to one of the following pins
(6, 9, 11, 12, 13 or 14) on the SAE J1962 diagnostic connector, or to an auxiliary pin which would need to be connected
to the vehicle via a cable that is unique to the vehicle.
The auxiliary pin on the interface shall be a female banana jack (see Section 6.4- Connection to Vehicle).
As well, short to ground capability on pin 15 is required. The following requirements shall be met by the power supply:
a. Minimum 5 V DC
b. Maximum 20 V DC
c. Resolution 0.1V DC
d. Accuracy ±2% of requested voltage
e. Maximum source current 150 mA
f. Maximum sink current 300mA (only for SHORT_TO_GROUND on pin 15).
g. Maximum 1 ms settling time (required for SCI protocol only, reference SAE J2610 Information Report)
h. Pin assignment software selectable
6.8 Pin Usage
Figure 3 indicates the possible uses for each pin of the SAE J1962 connector and for the auxiliary pin.
This figure also indicates the default condition for each pin, which is the required condition when the interface is connected to the vehicle,
and the condition to return to when the pin is no longer used to supply programming voltage, short to ground, or serial data communication.
For the following table, high impedance is defined as greater than 500 kΩ impedance relative to signal ground,
and as greater than 500 kΩ impedance relative to chassis ground.
