Reaction Module (REACM)
MPC5644A Microcontroller Reference Manual, Rev. 6
718
Freescale Semiconductor
Figure 23-19. Reaction channel architecture simplified diagram
The addresses stored in the Modulation Word are pointers to timers and threshold banks. HOD and LOD
provides the 3-bit field which controls the states, HIGH and LOW, respectively for the reaction channel
output pins. The reaction channel FSM selects the values for the output pins as well as the load signal used
to update those values. The modulation executed by the reaction channel is based on the feedback loop
provided by the ADC results. These results are routed to one side of a comparator while the other
comparator input receives the selected Threshold value from the threshold bank. The comparison result
indicates for the reaction channel FSM if the output pin value should be defined either by HOD or by LOD.
As a result a PWM is generated on the output pins. Note that since there are three independent outputs the
PWM signal can be generated on any output or even on several outputs at the same time. Usually a PWM
signal is generated in one of the outputs only, while the others outputs are used to control power supply
switching, for example.
Three wave forms are shown at the right side of
. On the top there is control signal from eTPU
which defines the boundaries of the modulated waveform. In the middle there is the PWM waveform
which is used to drive the power on and off at the load, thus generating the third waveform which
represents the current passing through the load.
DOFF[2:0] MODULATION_ADDR[5:0]
MM[1:0] SM[1:0]
HOD[2:0] LOD[2:0]
THRESPT[5:0]
HDOFFPT[3:0]
holdoff timer
Threshold value[15:0]
ADC
eTPU
initial value
Low selection
high selection
sequencing mode
modulation mode
FSM
load
sel
time out
compare
new result trigger
address
address
Reaction Channel
activate/deactivate
etpu window
Reaction PWM
Modulated current
output pins
feed back from the controlled load
v
t
t
i
t
v
}
+1
Summary of Contents for MPC5644A
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Page 1228: ...Decimation Filter MPC5644A Microcontroller Reference Manual Rev 6 1228 Freescale Semiconductor...
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