COREAI-XX Datasheet, PDF (22/25 Pages) Actel Corporation – CoreAI

CoreAI
ADC Operation
Control of the ADC within the AB macro in CoreAI is
accomplished by APB reads and writes. After a power-up
reset condition, the ADC will come out of its reset state
and commence with its internal calibration sequence.
When this calibration sequence has finished, the ADC
will be ready to use for conversions. Read the INT[1:0]
register bits to obtain status information relevant to the
ADC calibration.
The user must configure the analog quads
appropriately via the ACM interface to match the
required design-specific voltage, current, and
temperature ranges prior to performing ADC
conversions; failure to do so may result in damage to
the Fusion device. The SmartGen software can be used to
configure the analog quads and RTC.
ADC Control
A typical analog-to-digital conversion is shown starting
in Figure 7 and ending in Figure 8 on page 23. The steps
for performing an ADC conversion are as follows:
1. Read the ADC Status register to ensure that the ADC
is not busy calibrating or performing a conversion.
2. Write the desired ADC settings to ADC Control
register 1, including the voltage reference selection
(internal or external), mode selection (ADC
resolution), and clock divider settings.
3. Write the desired ADC settings to ADC Control
register 2, including the sample time control and
channel number to sample (1 of 32).
4. Set the Start Conversion bit to begin the
conversion process.
5. If a current or temperature monitor operation is
used on a corresponding AC or AT input pin, a write
must be done to set the corresponding current or
temperature monitor strobe high in ADC Control
register 3 or ADC Control register 4, respectively.
Refer to the Fusion datasheet for details on
external component connection requirements for
current and temperature monitoring.
6. Keep reading the high-order ADC Status register
until the ADC is not busy performing a conversion.
7. If a current or temperature monitor operation has
completed using a corresponding AC or AT input
pin, a write must be done to set the corresponding
current or temperature monitor strobe low in ADC
Control register 3 or ADC Control register 4,
respectively.
8. Read the low-order ADC Status register to obtain
the lower 8 bits of the resulting ADC conversion
data (the upper 4 bits of conversion data have
already been read from the high-order ADC Status
register).
ADC Conversion Starts
PCLK
PADDR[4:0] ADCStat(hi) ADCCtrl1(lo) ADCCtrl1(hi) ADCCtrl2(lo) ADCCtrl2(hi)
ADCStat(hi)
PWRITE
PSEL
PENABLE
PWDATA[7:0]
00
01
08
11
PRDATA[7:0]
00
60
Note: 8-bit APB reads and writes are shown.
Figure 7 • ADC Start of Conversion
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