Reaction Module (REACM)MPC5644A Microcontroller Reference Manual, Rev. 6Freescale Semiconductor 72723.5 Modulation ModesThis section describes the modulation modes provided by the reaction module.23.5.1 Threshold/Threshold modeThis mode is programmed by using REACM_MCWBx[MM] = 00. In this modulation mode the reactionchannel tries to maintain the ADC results between two threshold limits. The modulation actions are asfollows:• ADC result [THRESPT]: The reaction channel turns the outputs off by loading LOD[2:0] to thechannel outputs.• ADC result < [THRESPT + 1]: The reaction channel turns the outputs on by loading HOD[2:0] tothe channel outputs.• [THRESPT + 1] ADC result < [THRESPT]: The reaction channel keeps the outputs unchanged.Figure 23-27 indicates the threshold/threshold modulation mode.Figure 23-27. Threshold/threshold modulation modeThere can be overshoots or undershoots in the real application related to the threshold limits. This occursdue to following:1. Feedback values are periodically sampled thus can present gaps on the measured values, forexample when the sample occurs the value already passed the range defined by the limits.2. There is a delay between the sampling of feedback value and the reaction of the reaction channel.This is mainly caused by the ADC conversion time and its maximum sampling frequency.23.5.2 Threshold/Hold-off modeThis modulation mode is programmed by using REACM_MCWBx[MM] = 01. In this mode the outputpins are driven with HOD[2:0] until the ADC results matches or is greater than the programmed Threshold.The output controls are then driven with LOD[2:0] for a fixed amount of time defined by the hold-offtimer. Note that the upper threshold limit and the hold-off timer pointer are indicated by the modulationword in the REACM_MCR register.InjectortimeUpper LimitLower Limitfeedbackset output to LODset output to HODI
