NXP Semiconductors MPC5644A, Reference Manual, Page: 719 / 1735

Reaction Module (REACM)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 719
23.4.2 Modulation control words bank
The Modulation Control Word provides information about the modulation type to be performed and the
addresses for several address banks.
Figure 23-18 describes the REACM Modulation Control Word Bank
Registers (REACM_MWBK) and Figure 23-20 describes the interfaces of this submodule with some other
submodules in the Reaction Module. The informations stored in the Modulation Word are:
• Modulation control parameters for the reaction channel
• Threshold Value Register Bank address
• Hold-off bank address
• Shared Timer bank address
• DMA support
All channels share the information stored in the Modulation Control Word Bank, which provides a
size-effective implementation avoiding the duplication of information and allowing flexible
implementation. The sharing of modulation control words allows several channels to execute the same
modulation sequence.
The Modulation Control is designed to be used by all reaction channels as a centralized resource. However,
only one channel is able to access the Modulation bank at a given time. Therefore, there is a priority in the
selection of the channel that will have the access granted, but note that this condition does not occur too
often since ADC results are provided for one channel at a time.
An arbiter in the Modulation Control Word bank selects one of the channels which are requesting access
to a modulation word. The priority criteria is fixed and based on the channel number, considering Channel
0 the highest priority channel. The channel selected by the arbiter receives an acknowledge signal which
indicates that channel was selected and therefore can access the modulation word.
NOTE
In order to avoid an initial delay when processing a timer window start
event, the channel performs a speculative read operation of the first
modulation word when it is enabled (CHEN is configured). Therefore, when
the modulation cycle is triggered by the timer window start event, all needed
information for the modulation is already stored inside the channel.