Reaction Module Blockset

Reaction Module Setup for Injection Timing

Low impedance injector drivers circuits are based upon switching a MOSFET on and off at frequency to regulate load current. The high frequency switching allows the MOSFET to operate in its more thermally efficient saturated region. The circuits typically monitor load current and switch off when that current exceeds a certain threshold referred to as the “switch-off” current. For the 128-pin ECM for example, the switching is done in the hardware through a chopper circuit. This achieves a fixed peak hold current level.

By comparison, the switching for the ECM-OH is accomplished in software through the Reaction Module on the Freescale MPC5644. This gives greater flexibility to the application in setting the current limits at which the circuit will switch off (limits for max peak and max hold current) as well as the fixed amount of time for which the output will be switched off. The Reaction module must be defined, and the Reaction Channels configured for the required timing components and current thresholds to achieve the average current levels required in the application.

The standard PSP blocks (Injector Sequence, Dual PSP, Multiple PSP..) are supported on the ECM-OH, but configuration of the Reaction Module is Required for Injection on the ECM-OH. Peak-Hold timing is configured by the Reaction Module, and the peak-hold input port on the sequence blocks is ignored.

The Reaction Module Configuration blocks are located in the Module Configuration library of MotoHawk.

This article will give an overview of the Reaction Channel Blocks. Refer to the Block Help for each block for detailed descriptions of the block usage, limitations, and design considerations.

Reaction Module Definition block

This block MUST be placed in the model if injection is required. It defines the global configurations of Freescale Semiconductor’s Reaction Module. If this block is not placed in the model, the following build error will result.

ERROR: A ReactionModule with a ModuleResource of REACT was not found in the application descriptor.

Peak/Hold with Off Time (PHWOT) Controller and the Reaction Module off TimeDefinition block

Reaction Channels perform the load current modulation to achieve the desired average current and peak/hold times. Once the Reaction Module is Defined, the Reaction Channel Behaviors must Be configured. The Peak/Hold with Off Time (PHWOT) Controller block Defines the Peak Threshold and Hold Threshold values used for modulation. The Reaction Module off Time Definition block defines the fixed amount of time the channel will turn off, once the threshold value is reached. As an example, one MotoHawk Reaction Channel Contoller Peak Hold with Off Time block is configured, and the Peak Threshold and Hold Threshold are input into the block. Detect Threshold is for fault detection. Also, two Reaction Module Off Time Definition blocks are used in this example. One is controlling the off time for the peak section of the injector output, and the other is controlling the off time for the hold portion. This could be configured differently to fit the specific application needs.