Motorola MC68HC908AB32, Technical Data Manual

Page: 238 / 392

Analog-to-Digital Converter (ADC)
Technical Data MC68HC908AB32
—
Rev. 1.0
238
Analog-to-Digital Converter (ADC) MOTOROLA
ADICLK — ADC Input Clock Select Bit
ADICLK selects either the bus clock or CGMXCLK as the input clock
source to generate the internal ADC clock. Reset selects CGMXCLK
as the ADC clock source.
If the external clock (CGMXCLK) is equal to or greater than 1 MHz,
CGMXCLK can be used as the clock source for the ADC. If
CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as
the clock source. As long as the internal ADC clock is at
approximately 1 MHz, correct operation can be guaranteed.
1 = Internal bus clock
0 = External clock (CGMXCLK)
Table 14-2. ADC Clock Divide Ratio
ADIV2 ADIV1 ADIV0 ADC Clock Rate
0 0 0 ADC input clock
÷
1
0 0 1 ADC input clock
÷
2
0 1 0 ADC input clock
÷
4
0 1 1 ADC input clock
÷
8
1 X X ADC input clock
÷
16
X = don’t care
ADC input clock frequency
ADIV[2:0]
----------------------------------------------------------------------- 1MHz =