Enhanced Queued Analog-to-Digital Converter (EQADC)MPC5644A Microcontroller Reference Manual, Rev. 61072 Freescale SemiconductorCFIFOs can be configured in single-scan or continuous-scan mode. When a CFIFO is configured insingle-scan mode, the EQADC scans the CQueue one time. The EQADC stops transferring commandsfrom the triggered CFIFO after detecting the EOQ bit set in the last transfer. After an EOQ bit is detected,software involvement is required to rearm the CFIFO so that it can detect new trigger events.When a CFIFO is configured for continuous-scan mode, the whole CQueue is scanned multiple times.After the detection of an asserted EOQ bit in the last command transfer, command transfers can continueor not depending on the mode of operation of the CFIFO.CFIFO0 has a special configuration option to allow a repetitive sequence of conversion commands(streaming mode) with high priority characteristics (abort operation) or not. This feature is useful with theimmediate conversion command feature that allows the immediate execution of a conversion command ora sequence of commands with critical timing even with the possibility of abortion of some current ADCconversion in progress. The aborted command is stored and executed again as soon as the critical timingcommands have been finished.The multiple Result FIFOs (RFIFOs) can receive data from the on-chip ADCs, from an off-chip externaldevice or from an on-chip companion module. Data from the on-chip ADCs can be routed to the sideinterface, processed by the on-chip companion module and then routed back through the side interface tothe RFIFOs.25.6.2 Data Flow in EQADC25.6.2.1 Overview and Basic TerminologyFigure 25-48 shows how command data flows inside the EQADC system. A Command Message is thepredefined format at which command data is stored on the CQueues. A Command message has 32 bits andis composed of two parts: a CFIFO header and an ADC Command. Command messages are moved fromthe CQueues to the CFIFOs by the host CPU or by the DMAC as they respond to interrupt and DMArequests generated by the EQADC. The EQADC generates these requests whenever a CFIFO is not full.The FIFO Control Unit will only transfer to a CBuffer the ADC command part of the Command Message.Information in the CFIFO header together with the upper bit of the ADC command is used by the FIFOControl Unit to arbitrate which triggered CFIFO will be transferring the next command. Since commandtransfer through the serial interface can take significantly more time than a parallel transfer to the on-chipADCs, command transfers for on-chip ADCs occur concurrently with the ones through the serial interface.
