MC68HC908KX8 Datasheet, PDF (248/310 Pages) Motorola, Inc – Microcontrollers

Analog-to-Digital Converter (ADC)
17.4.3 Conversion Time
Conversion starts after a write to the ADSCR (ADC status control
register, $003C) and requires between 16 and 17 ADC clock cycles to
complete. Conversion time in terms of the number of bus cycles is a
function of CGMXCLK frequency, bus frequency, the ADIV prescaler
bits, and the ADICLK bit. For example, with a CGMXCLK frequency of
8 MHz, bus frequency of 2 MHz, and fixed ADC clock frequency of 1
MHz, one conversion will take between 16 and 17 µs and there will be
32 bus cycles between each conversion. Sample rate is approximately
60 kHz.
Refer to 20.10 Trimmed Accuracy of the Internal Clock Generator.
Conversion time = ¹⁶^t^{o 1}⁷^AD^C^c^loc^k^cy^cl^es
ADC clock frequency
Number of bus cycles = conversion time x bus frequency
17.4.4 Continuous Conversion
In continuous conversion mode, the ADC data register will be filled with
new data after each conversion. Data from the previous conversion will
be overwritten whether that data has been read or not. Conversions will
continue until the ADCO bit (ADC status control register, $003C) is
cleared. The COCO bit is set after the first conversion and will stay set
until the next write of the ADC status and control register or the next read
of the ADC data register.
17.4.5 Accuracy and Precision
The conversion process is monotonic and has no missing codes.
See 20.10 Trimmed Accuracy of the Internal Clock Generator for
accuracy information.
Technical Data
248
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
Analog-to-Digital Converter (ADC)
MOTOROLA