NXP Semiconductors MPC5644A, Reference Manual, Page: 1091 / 1735

Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1091
• CFIFO_DEPTH is the number of entries contained in a CFIFO - four in this implementation.
When CFS x in Section 25.5.2.12, EQADC CFIFO Status Register (EQADC_CFSR) , is TRIGGERED, the
EQADC generates the proper control signals for the transfer of the entry pointed by Transfer Next Data
Pointer. CFUFx
in Section 25.5.2.9, EQADC FIFO and Interrupt Status Registers (EQADC_FISR) , is set
when a CFIFOx underflow event occurs. A CFIFO underflow occurs when the CFIFO is in TRIGGERED
state and it becomes empty. No commands will be transferred from an underflowing CFIFO, nor will
command transfers from lower priority CFIFOs be blocked. CFIFOx is empty when the Transfer Next
Data Pointer x equals the Push Next Data Pointer x and CFCTRx is zero. CFIFOx is full when the Transfer
Next Data Pointer x equals the Push Next Data Pointer x and CFCTRx is not zero.
When the EQADC completes the transfer of an entry from CFIFOx: the transferred entry is popped from
CFIFOx, the CFIFO counter CFCTR in the
Section 25.5.2.9, EQADC FIFO and Interrupt Status Registers
(EQADC_FISR) , is decremented by one, and Transfer Next Data Pointer x is incremented by one (or
wrapped around) to point to the next entry in the CFIFO. The transfer of entries bound for the on-chip
ADCs is considered completed when they are stored in the appropriate CBuffer. The transfer of entries
bound for the external device is considered completed when the serial transmission of the entry is
completed.
When the EQADC_CFPRx is written and CFIFOx is not full, the CFIFO counter CFCTRx is incremented
by one, and the Push Next Data Pointer x then is incremented by one (or wrapped around) to point to the
next entry in the CFIFO.
When the EQADC_CFPRx is written but CFIFOx is full, the EQADC will not increment the counter value
and will not overwrite any entry in CFIFOx.