M220 Technical Specification
29T-068432TK-05

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.

The power supply pin (V_PWR A2) and the ground pin (V_GND A31) are both rated to 40A.

The ECU V_GND (pin A31) and sensor ground (pins A40+A41) are directly connected together via a ground plane in the ECU PCB. The ECU case is capacitively coupled to V_GND.

The ECU is designed for 12V or 24V vehicles, with various modes of operation based on the voltage (see Table 1.1, “Specification”). The ECU is protected against reverse supply connection. All inputs and outputs are protected against short-to-V_PWR or short-to-V_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 A2) and key position (ignition sense) input (pin A26) are asserted. The key position input (pin A26) 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 high will hold power when the key position input is opened, setting it low will allow the ECU to power off when the key position input is opened.

The ECU provides one external sensor power supply (pin A25). The sensor supply can be switched off to allow the application software to perform intrusive diagnostics on sensors.

The power supply is monitored by an analogue input which can be used to check for short circuits and measure the exact output voltage for use with ratio-metric sensors.

The analogue inputs (pins A3, A5, A7, A10, A12, A13, A14, A15, A18, A19, A20 and A21) sample voltage with varying resolution and range. See the pin information for more details.

The ECU power arrangement is shown in Figure 4.2, “VREF arrangement”. The figure shows the relationship between the internal 5V V_REF and ground, the external sensor supply and ground, and the analogue inputs.

Figure 4.2. V_REF arrangement

The internal low precision 5V reference supplies the reference pin on the ADC. The 5V reference is divided down to 4.95V to provide the external sensor supply. The exact voltage being produced can be read on a direct (unscaled) ADC channel. The sensor ground is a nominal 0V, but may be slightly above this due to voltage drop across the protection device.

The exact voltage on the analogue input pin can be read on a direct (unscaled) ADC channel. Standard 0-5V inputs are passed directly to the ADC with no scaling.

Some analogue input pins are internally pulled up to the sensor power supply (pin A25). If the sensor supply is not enabled, floating inputs will fluctuate when read by the ADC. The sensor supply must be enabled for resistance measurements made on any of these channels.

The analogue input pins A4, A6, A8 and A9 have conditioning circuitry for interfacing to Variable Reluctance (VR) sensors. The VR signal is amplified, processed to determine an adaptive threshold used in noise reduction, and then processed to determine zero crossings representing the center of teeth. The input chip is also capable of processing in Hall effect mode however.

Each of these inputs has a corresponding "Hall-VRS Select" internal digital output signal to select VR mode or Hall effect mode. Set to 1 for Hall effect, 0 for VRS-style input.

A second "Hall input bias" internal digital output signal is available for each of these inputs. For VRS-style input this has no effect and can be ignored. For Hall-effect, set to 1 for a slightly higher input voltage threshold.

In VR mode, once the VR input signal voltage rises above an adaptive threshold, the zero crossing comparator is armed. Arming the comparator this way provides robust noise immunity to the input VR signal, preventing false triggers from occurring due to a broken tooth or an off-center tooth wheel.

The peak threshold level is set to a third of the peak of the previous cycle of the input VR signal. As the sensor signal peak voltage rises or falls, the adaptive peak threshold voltage also increases by the same ratio. If the input signal voltage remains lower than the adaptive peak threshold for more than 85ms, an internal watchdog timer drops the threshold level to a default minimum threshold. This ensures pulse recognition recovers even in the presence of intermittent sensor connection.

Once armed, the zero crossing detection logic generates a digital (rising) edge when the positive input signal falls below the negative input signal. For single-ended inputs (pins A4 and A6) this occurs when the input signals falls below ground. This zero crossing point corresponds to the center of the gear-tooth (provided the sensor is wired the right way round) and is the most reliable marker for position/angle-sensing applications.

The VR input circuitry introduces a phase offset as an artifact of signal filtering. The phase shift causes the digital tooth edge representing the tooth center to occur some time after the actual tooth center. The time between the digital tooth edge and the actual tooth center increases as the frequency of the input signal increases.

Pins A8+A9 are a differential input pair. In order to use these as a single ended input, pin A9 should be connected to sensor ground (pins A40+A41).

The conditioning circuitry for pins A4, A6, A8 and A9 invert the logical sense of the inputs. In VRS mode, a logic 0 is reported from when the interface is armed until the zero-crossing point, and a logic 1 is reported from the zero-crossing point until the interface is next armed. In Hall effect mode, a logic 1 is reported if the signal is less than the threshold voltage and a logic 0 is reported if it is greater than the threshold voltage. For the differential input on pins A8+A9, the signal here means the positive input signal on pin A8 minus the negative input signal on pin A9.

The peak-to-peak voltage range for each VR input varies with temperature:

These voltage limits are with full power loading of the outputs. The voltage limits will be higher with lighter load conditions.

The digital inputs (pins A22, A38, A39 and A42, A11 and A26) sense the binary state based on the pin voltage and a threshold.

The digital outputs (pins A16, A17, A29, A32, A33, A34, A35, A36, A37, A44, A45 and A46) reflect a mixture of high-side and low-side drivers. Pin A16 is configured as a high-side — the ECU switches this output pin to V_PWR and the actuator is connected to the output pin and ground.

On some variants of the M220-000, the digital outputs for pins A17, A29, A32 and A33 have current feedback channels populated. The current feedback channels can be read as analogue inputs, see Table 3.1, “Internal signals” for details.

Figure 4.3. High-side switching arrangement for digital outputs

Pins A17, A29, A32, A33, A34, A35, A36, A37, A44, A45 and A46 are configured as low-side — the ECU switches the output pin to ground, the load is connected to the output pin and the battery.

Figure 4.4. Low-side 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 analogue monitor channel. The analogue monitor channel measures the actual voltage at the pin after scaling.

When the pin is used as a PWM, there are two possible uses for such a feedback:

When the pin is used as a plain digital output, feedback is used as follows:

The digital outputs apart from A16 and A45 are self protecting; in case of a fault the outputs will automatically switch off, and once they recover, switch on again.

Output A45 has an over-current trip state monitor. In normal operation the internal over-current trip channel will be one. 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 zero.

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.

The high-side output (pin A16) has a number of internal monitor signals (voltage, current and current trip). In normal operation the internal over-current trip channel will be one. 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 zero.

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.

The relationship between the high-side output's (pin A16) current monitor and the ADC voltage is non-linear below 0.5A. Refer to Table 4.4, “High-side digital output current monitor” for correlation between current and voltage.

The H-bridge outputs (pins A30+A1) are controlled through the pdx_HBridge_Output Simulink block or the pdx_hbridge_output() C-API function.

Figure 4.5. H-bridge arrangement

The H-Bridge can be driven in four modes:

The frequency and the duty cycle of operation are controlled by the application. There are monitor inputs to check the output pin state.

The H-bridge outputs include an H-bridge Ready signal which can be used to determine faults that are internal to the H-bridge IC.

The H-bridge Ready signal is interpreted as follows:

The CAN busses (pins A23+A24 and A28+A43) are implemented using high-speed CAN transceivers. CAN bus 1 (pins A23+A24) has terminating resistors fitted, CAN bus 0 (pins A28+A43) doesn't.

The ECU supports different memory configurations for application, calibration and RAM sizes, some of which require external calibration RAM (see Section 4.17, “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 selects which mode to enter when it is powered up by measuring the external FEPS A27 pin.

The ECU also uses the FEPS input (pin A27) as an output to flash an optional LED. The LED is connected between V_PWR (pin A2) and FEPS (pin A27). Note that the pin use as FEPS input or as lamp output is mutually exclusive.

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 of marks, or on and off pulses as follows:

Figure 4.6. 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:

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.

To support a variety of sensors and actuators, the ECU is pre-populated with a default selection of components with varying voltage range, pull strengths, filtering and other characteristics. In some cases, the default component selection will not meet the requirements of all customers. Within design constraints, Pi can modify the ECU components to adjust these characteristics as build options. Contact Pi for further information.