Z8 Encore! XP® 4K Series
Product Specification
116
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If the internal voltage reference must be output to a pin, set the REFEXTbit to 1.
The internal voltage reference must be enabled in this case.
Write the REFSELLbit of the pair {REFSELH, REFSELL} to select the internal
voltage reference level or to disable the internal reference. The REFSELHbit is
contained in the ADC Control/Status Register 1.
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Set CENto 1 to start the conversion.
5. CENremains 1 while the conversion is in progress. A single-shot conversion requires
5129 system clock cycles to complete. If a single-shot conversion is requested from an
ADC powered-down state, the ADC uses 40 additional clock cycles to power up
before beginning the 5129 cycle conversion.
6. When the conversion is complete, the ADC control logic performs the following
operations:
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13-bit two’s-complement result written to {ADCD_H[7:0], ADCD_L[7:3]}.
CENresets to 0 to indicate the conversion is complete.
If the High and Low alarms are disabled, an interrupt request is sent to the
Interrupt Controller denoting conversion complete.
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If the High alarm is enabled and the ADC value is higher than the alarm threshold,
an interrupt is generated.
If the Low alarm is enabled and the ADC value is lower than the alarm threshold,
an interrupt is generated.
7. If the ADC remains idle for 160 consecutive system clock cycles, it is automatically
powered-down.
Continuous Conversion
When configured for continuous conversion, the ADC continuously performs an analog-
to-digital conversion on the selected analog input. Each new data value over-writes the
previous value stored in the ADC Data registers. An interrupt is generated after each con-
version.
In CONTINUOUS mode, ADC updates are limited by the input signal bandwidth of the
ADC and the latency of the ADC and its digital filter. Step changes at the input are not
immediately detected at the next output from the ADC. The response of the ADC (in all
modes) is limited by the input signal bandwidth and the latency.
Caution:
Follow these steps for setting up the ADC and initiating continuous conversion:
1. Enable the desired analog input by configuring the general-purpose I/O pins for
alternate function. This action disables the digital input and output driver.
2. Write the ADC High Threshold Register and ADC Low Threshold Register if the
alarm function is required.
PS022815-0206
Analog-to-Digital Converter
ZILOG [ ZILOG, INC. ]
