Z8F021ASH020SC datasheet(135/276 Pages) ZILOG

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PS022815-0206

Analog-to-Digital Converter

Z8 Encore! XP® 4K Series

Product Specification

116

–

If the internal voltage reference must be output to a pin, set the REFEXT bit to 1.

The internal voltage reference must be enabled in this case.

–

Write the REFSELL bit of the pair {REFSELH, REFSELL} to select the internal

voltage reference level or to disable the internal reference. The REFSELH bit is

contained in the ADC Control/Status Register 1.

–

Set CEN to 1 to start the conversion.

5. CEN remains 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:

–

13-bit two’s-complement result written to {ADCD_H[7:0], ADCD_L[7:3]}.

–

CEN

resets 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.

–

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.

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.

Caution:

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