M461 Technical Specification
29T-068148TK-03

This technical specification relates to the following ECU variant:

Various input and output functionality is supported where some pins may be capable of more than one function. Some functions require a combination of pins but not all pin combinations are possible.

Connector packs can be ordered from Pi. Individual connector components can be ordered from Pi or from various manufacturers.

Connector packs can be ordered from Pi. Individual connector components can be ordered from Pi or from various manufacturers.

The power supply pins (V_PWR A10+A20+A30) are connected internally in parallel. Similarly for the ground pins (V_GND C1+C2+C11+C12+C38).

The power supply pins are each individually rated to 7A and can be connected in parallel to provide a higher rating (e.g., using two pins gives 14A, three pins gives 21A, etc.). The maximum supply is 21A. All power supply pins are connected internally in parallel (similarly for the ground pins).

The ECU is designed for 12V or 24V vehicles. Some ECU functionality (e.g., output drivers) work only between 7.5V and 32V. The ECU is protected against reverse supply connection. All inputs and outputs are protected against short-to-V_PWR or short-to-_GND over normal operating range.

The ECU power arrangement is shown in Figure 4.1, “Switching arrangement for main power supply”.

Figure 4.1. Switching arrangement for main power supply

The ECU is powered up when the power supply pins (V_PWR A10+A20+A30) and key position (ignition sense) input (pin A12) are asserted. The key position input (pin A12) can be read as a digital input.

This arrangement allows for the ECU application software to hold the ECU on after the external key position input is opened, allowing, for example, non-volatile memory processing to occur. For the ECU to hold power the internal DOT hold-PSU channel needs to be asserted. Setting this internal channel low will hold power when the key position input is opened, setting it high will allow the ECU to power off when the key position input is opened.

Unlike some other ECUs, the M461-000 does provide an actuator supply.

The ECU provides four external sensor power supplies (pins A8, A18, C8 and C18) and common sensor ground (pins A9, A19, C9 and C19).

The sensors supplies can be individually switched off to allow the application software to perform intrusive diagnostics on sensors. Each output is monitored by an internal analogue input channel which can be used to check for short circuits and measure the exact output voltage for use with ratio-metric sensors.

The output voltage is guaranteed to never reach full scale in normal operation, hence a full scale indication should be taken to indicate a suspected short to battery. The value read from the voltage monitor when the corresponding PSU is enabled should be interpreted as follows:

The value read from the common sensor ground voltage monitor should be interpreted as follows:

The sensor ground feedback can also be used in normal operation by the application software to provide a precision ground reference for ratio-metric measurements.

The analogue inputs (pins A16, A22, A23, A24, A28, A32, A33, A34, C3, C4, C6, C13, C14, C16, C21, C22, C23, C24, C25, C31, C32, C33 and C35) sample voltage with varying resolution and range. See the pin information for more details. Some of the analogue inputs have additional characteristics, as detailed in the following sections.

Although the ECU does not include thermocouple inputs, like some other ECUs, the M461-000 does retain the cold-junction temperature input which can be utilised as the internal temperature of the ECU.

The relationship between temperature and the ADC voltage (V_ADC) and ADC counts (C_ADC) for the internal temperature sensor is:

over a range of -40°C to +125°C.

The internal accelerometer channels (AIN accelerometer-x, AIN accelerometer-y and AIN accelerometer-z) have a zero point of 1.65V and give an output swing of 600mV/g. The relationship between acceleration and the ADC voltage (V_ADC) is:

The full scale range of the accelerometer is ±2g so V_ADC will never reach 0V or 5V in normal operation.

The internal gyroscope channels (AIN gyroscope-x, AIN gyroscope-y and AIN gyroscope-z) have a zero point of 2.5V and give an output swing of ±2.25V for rotation rates in the range ±50°/s. The relationship between rotation and the ADC voltage (V_ADC) is:

In addition to their analogue outputs, the gyroscopes have two self test signals (internal channels DOT gyro-self-test-1 and DOT gyro-self-test-2). Asserting these signals high introduces an offset to V_ADC for diagnostic purposes.

Asserting internal channel DOT gyro-self-test-1 high causes V_ADC to change -1.9V. Asserting internal channel DOT gyro-self-test-2 high causes an opposite change of +1.9V. The self-test response follows the viscosity temperature dependence of the package atmosphere, approximately 0.25%/°C.

The gyroscope devices provide a single temperature signal (internal channel AIN gyroscope-temperature. This signal may be used by the application software to compensate for drift of the gyroscopes. The relationship between temperature and the ADC voltage (V_ADC) for the gyroscope temperature sensor is:

over a range of -40°C to +125°C. Refer to the ADXRS614 data-sheet from Analog Devices for further information on temperature calibration.

The accelerometer and gyroscope orientation is pictured below:

Figure 4.2. Orientation of accelerometer and gyroscope axes

The inputs work on a voltage threshold. If the external pin is above the threshold voltage the input will be 0, if the external pin is below the threshold the input will be 1 (i.e. signal is inverted between the external pin and the software).

The digital outputs (pins A1, A5, A7, A11, A15, A17, A21, A25, A31, A35, C5, C10, C15 and C20) are low-side drivers. That is, the ECU switches the output pin to ground, the actuator is connected to the output pin and the battery.

Figure 4.3. Switching arrangement for digital outputs

The low-side digital outputs contain internal monitoring circuitry that provides diagnostic information. However, as a consequence a small leakage current will flow through the actuator when the low-side output driver is turned off. Refer to Table 4.3, “Low-side digital output leakage current” for typical leakage currents at specified operating voltages.

The actual state of an output pin can be monitored using a corresponding internal digital monitor and internal analogue monitor channel. The digital monitor channel simply reflects the on or off state of the actual output. The analogue monitor channel measures the actual voltage at the pin after scaling.

The over-current trip state of an output pin can be monitored using a corresponding internal over-current monitor channel. In normal operation the internal over-current trip channel will be 1. If the output channel experiences an over-current, the output channel will be forced off by the ECU and the over-current trip channel will be set to 0.

The over-current trip latch can be cleared and the tripped outputs enabled by the pss_OvercurTripReset Simulink block or by calling the pss_overcur_trip_reset() C-API function.

Some of the internal and external inputs and outputs are classed as serial. The connector pinout tables and internal channel tables above specify whether a pin or channel is serial or not.

When a serial input is read, the measurement reflects the value of the input taken last time the application task ended. I.e., the value of the input is delayed by one cycle of the task period. When a serial output is set, the driven state is updated at the end of the current application task. I.e., there is a delay between requesting a change in the output state, and the output state honoring that request.

The CAN buses (pins A37+A36 and C37+C36) are implemented using high-speed CAN transceivers. Each CAN bus has terminating resistors fitted. Fleet and developer ECUs support two CAN buses (see the pin details for more information).

The ECU supports different memory configurations for application, calibration and RAM sizes, some of which require external calibration RAM (see Section 4.18, “Memory — calibration capabilities”).

The ECU supports non-volatile memory storage in Flash. Battery backed RAM is not supported.

The processor's Flash memory is split into small and large memory blocks. The application and calibration are stored in large blocks, whilst DTC information, freeze frames and so on are stored in small blocks.

The largest Flash block can take up to approximately 7.5 seconds to erase. This occurs in an environment where the Flash has been erased and programmed many times at its temperature extreme. The typical erase time is smaller, especially at ambient temperatures. Reprogramming an ECU (where many large blocks would be erased), or storing DTC information across power cycles, can therefore take some time. Users and applications should take this into consideration.

The minimum number of erase cycles is approximately 1,000 for large Flash blocks and 100,000 for small Flash blocks. This occurs in an environment where the Flash has been erased and programmed many times at its temperature extreme. The typical number of erase cycles is larger, especially at ambient temperatures.

The minimum data retention is approximately 5 years for blocks which have been erased less than 100,000 times, and approximately 20 years for blocks which have been erased less than 1,000 times.

The information about the Flash has been taken from Freescale's MPC5534 Microcontroller Data Sheet document, revision 4 (dated Mar 2008).

The ECU supports both offline calibration (where all of the ECU's calibration memory is reprogrammed whilst the application is stopped) and online calibration (where individual calibrations can be modified whilst the application runs). These calibration capabilities are supported through two ECU types:

The ECU can run in one of two system modes: reprogramming mode and application mode. In reprogramming mode, the ECU can be reprogrammed with application software from a calibration tool. In application mode, the ECU runs the programmed application software. The ECU enters reprogramming mode either by measuring the external FEPS A2 pin at power up, or when attempting to reflash over CCP when the application is not inhibiting reflashing.

The ECU has a dedicated external pin (A27) for flashing a lamp. The flash sequence represents a set of codes. Each code is a three digit number, where each digit is flashed a number of times equal to its value.

An example would be the flash sequence for code 113. The flash sequence is broken down into a series on marks, or on and off pulses as follows:

Figure 4.4. Flash code sequence

Each of the marks lasts for a specific duration:

After the end code mark, the ECU will either flash the next code, or return to the start of the list and flash the first code. The ECU always has at least one code to flash.

Each code represents information about the ECU state. If there is no flash sequence, or a malformed flash sequence, then the ECU is malfunctioning. Otherwise, the flash sequence will represent one of the following codes:

Developer units have the capability to accept calibration changes while the application software is running. Fleet units do not have this capability.

The ECU closely adheres to the IEEE-754 for floating point numbers.

When using Simulink, floating point Simulink models are supported — all calculations are performed using single-precision (even if the model uses double-precision, the ECU performs calculations using single-precision).

When using the C-API, floating point applications are supported — all calculations are performed using single or double precision, as determined by the application code (although double precision will incur some software overhead — see the compiler reference manual for further details).

The rounding mode is set to round-to-nearest. In some conditions, the ECU will not adhere to the IEEE-754 standard:

The ECU does not generate ±Inf, NaN or a denormalised number as the result of a calculation.