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Enhanced Queued Analog-to-Digital Converter (EQADC)
Freescale Semiconductor
27-117
PXR40 Microcontroller Reference Manual, Rev. 1
27.8.1.1
EQADC Initialization
The following steps provide an example about how to configure the EQADC controls and how to initialize
the on-chip ADCs. In this example, all conversion commands will be transferred through CFIFO0.
1.
Load all required configuration commands in the RAM in such way that they form a queue; this
data structure will be referred below as CQueue0.
shows an example of a CQueue able
to configure the on-chip ADCs at the same time. Although, this example uses the DMAC to store
commands in CFIFO0, configuration commands could have also been directly written to the
CFIFO0 push register.
2. Select source driving EQADC hardware trigger ports (ETRIG). Before proceeding to next step,
allow some time (minimum of two platform clocks - filter period is set to minimum after reset) so
that the logic level at the source is filtered and reaches the EQADC control logic.
NOTE
ETRIG ports could be driven by an external pin or by the output port of
other blocks in the device, such as timers. In order to avoid unexpected
triggering of CFIFOs in hardware trigger modes, the source driving the
ETRIG port must be selected and set to a known logic level before putting
the CFIFOs into the WAITING FOR TRIGGER state.
3.
Configure
Section 27.6.2.2, EQADC External Trigger Digital Filter Register (EQADC_ETDFR)
.
4.
Configure the DMAC to transfer data from CQueue0 to CFIFO0 in the EQADC.
5.
Configure
Section 27.6.2.6, EQADC Interrupt and DMA Control Registers (EQADC_IDCR)
a.
Set CFFS0 to configure the EQADC to generate a DMA request to load commands from
CQueue 0 to the CFIFO0.
b.
Set CFFE0 to enable the EQADC to generate a DMA request to transfer commands from
CQueue0 to CFIFO0; Command transfers from the RAM to the CFIFO0 will start immediately.
c.
Set EOQIE0 to enable the EQADC to generate an interrupt after transferring all of the
commands of CQueue0 through CFIFO0.
6.
Configure
Section 27.6.2.5, EQADC CFIFO Control Registers (EQADC_CFCR)
3
Software-triggered
CQueue
every 3.9 ms
3
Command triggered by
software strategy
4
Repetitive
angle-based
CQueue
every 625
s
7
Airflow read every 30
degrees at 8000 RPM
5
Slow repetitive
time-based CQueue
every 100 ms
10
Temperature sensors
Table 27-46. Application of Each CQueue (continued)
CQueue
Number
CQueue Type
Running Speed
Number of
Contiguous
Conversions
Example
Summary of Contents for PXR4030
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