MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
19-3
The eQADC consists of the FIFO control unit which controls the CFIFOs and the RFIFOs, two ADCs with
associated control logic, and the eQADC synchronous serial interface
(eQADC SSI) which allows
communication with an external device. There are 6 CFIFOs and 6 RFIFOs, each with 4 entries.
The FIFO control unit performs the following functions:
•
Prioritizes the CFIFOs to determine what CFIFOs will have their commands transferred
•
Supports software and hardware triggers to start command transfers from a particular CFIFO
•
Decodes command data from the CFIFOs, and accordingly, sends these commands to one of the
two on-chip ADCs or to the external device
•
Decodes result data from on-chip ADCs or from the external device, and transfers data to the
appropriate RFIFO
The ADC control logic manages the execution of commands bound for on-chip ADCs from the CFIFOs
and with the RFIFOs via the result format and calibration submodule. The ADC control logic performs the
following functions:
•
Buffers command data for execution
•
Decodes command data and accordingly generates control signals for the two on-chip ADCs
•
Formats and calibrates conversion result data coming from the on-chip ADCs
•
Generates the internal multiplexer control signals and the select signals used by the external
multiplexers
The eQADC SSI allows for a full duplex, synchronous, serial communication between the eQADC and an
external device.
also depicts data flow through the eQADC. Commands are contained in system memory in a
user-defined queue data structure. Command data is moved from the user-defined command queue to the
CFIFOs by either the host CPU or by the eDMA. After a CFIFO is triggered and becomes the highest
priority, CFIFO command data is transferred from the CFIFO to the on chip ADCs, or to the external
device. The ADC executes the command, and the result is moved through the result format and calibration
submodule and to the RFIFO. The RFIFO target is specified by a field in the command that initiated the
conversion. Data from the external device bypasses the result format and calibration submodule and is
moved directly to its specified RFIFO. When data is stored in an RFIFO, data is moved from the RFIFO
by the host CPU or by the eDMA to a data structure in system memory depicted in
as a
user-defined result queue.
For users familiar with the QADC, the eQADC system upgrades the functionality provided by that
module. Refer to
Section 19.5.7, “eQADC versus QADC
,” for a comparison between the eQADC and
QADC.
19.1.3
Features
The eQADC includes these distinctive features:
•
Two independent on-chip RSD cyclic ADCs
— 12 Bit AD Resolution.
— Targets up to 10 bit accuracy at 400 kilosamples per second (ADC_CLK=6MHz) and 8 bit
accuracy at 800 kilosamples per second (ADC_CLK=12MHz) for differential conversions.
— Differential conversions (range -2.5V to +2.5V).
— Single-ended signal range from 0 to 5V.
— Sample times of 2 (default), 8, 64, or 128 ADC clock cycles.
— Provides sample time stamp information when requested.
Summary of Contents for MPC5553
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