Z8 Encore! XP® F08xA Series
Product Specification
110
put values across the entire 11-bit range, from -1024 to +1023. In SINGLE-ENDED mode,
the output generally ranges from 0 to +1023, but offset errors can cause small negative
values.
The ADC registers return 13 bits of data, but the two LSBs are intended for compensation
use only. When the compensation routine is performed on the 13 bit raw ADC value, two
bits of resolution are lost because of a rounding error. As a result, the final value is an 11-
bit number.
Automatic Powerdown
If the ADC is idle (no conversions in progress) for 160 consecutive system clock cycles,
portions of the ADC are automatically powered down. From this powerdown state, the
ADC requires 40 system clock cycles to powerup. The ADC powers up when a conversion
is requested by the ADC Control register.
Single-Shot Conversion
When configured for single-shot conversion, the ADC performs a single analog-to-digital
conversion on the selected analog input channel. After completion of the conversion, the
ADC shuts down. The steps for setting up the ADC and initiating a single-shot conversion
are as follows:
1. Enable the acceptable analog inputs by configuring the general-purpose I/O pins for
alternate function. This configuration disables the digital input and output drivers.
2. Write the ADC High Threshold Register and ADC Low Threshold Register if the alarm
function is required.
3. Write the ADC Control/Status Register 1 to configure the ADC
–
Write to BUFMODE[2:0] to select SINGLE-ENDED or DIFFERENTIAL mode,
as well as unbuffered, buffered, 20x buffered gain (in DIFFERENTIAL mode
only) or TRANSIMPEDANCE mode
–
–
If the alarm function is required, set ALMHENand/or ALMLEN
Write the REFSELHbit 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.
4. Write to the ADC Control Register 0 to configure the ADC and begin the conversion.
The bit fields in the ADC Control register can be written simultaneously:
–
–
Write to the ANAIN[3:0] field to select from the available analog input sources
(different input pins available depending on the device)
Clear CONTto 0 to select a single-shot conversion.
PS024705-0405
P R E L I M I N A R Y
Analog-to-Digital Converter
ZILOG [ ZILOG, INC. ]
