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.