MC68HC908LJ12 Datasheet, PDF (313/413 Pages) Freescale Semiconductor, Inc – 8-bit microcontroller units

Analog-to-Digital Converter (ADC)
15.8.3 ADC Clock Control Register
The ADC clock control register (ADCLK) selects the clock frequency for
the ADC.
Address: $003F
Read:
0
0
ADIV2 ADIV1 ADIV0 ADICLK MODE1 MODE0
Write:
R
Reset: 0
0
0
0
0
1
0
0
= Unimplemented
R = Reserved
Figure 15-9. ADC Clock Control Register (ADICLK)
ADIV[2:0] — ADC Clock Prescaler Bits
ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide
ratio used by the ADC to generate the internal ADC clock.
Table 15-2 shows the available clock configurations. The ADC clock
should be set to between 32kHz and 2MHz.
Table 15-2. ADC Clock Divide Ratio
ADIV2 ADIV1
0
0
0
0
0
1
0
1
1
X
X = don’t care
ADIV0
0
1
0
1
X
ADC Clock Rate
ADC input clock ÷ 1
ADC input clock ÷ 2
ADC input clock ÷ 4
ADC input clock ÷ 8
ADC input clock ÷ 16
ADICLK — ADC Input Clock Select Bit
ADICLK selects either bus clock or CGMXCLK as the input clock
source to generate the internal ADC clock. Reset selects CGMXCLK
as the ADC clock source.
Technical Data
314
Analog-to-Digital Converter (ADC)
MC68HC908LJ12 — Rev. 2.1
Freescale Semiconductor