
Input/Output Registers
MC68HLC908QY/QT Family Data Sheet, Rev. 3
Freescale Semiconductor
45
3.7.3 ADC Input Clock Register
This register selects the clock frequency for the ADC.
ADIV2–ADIV0 — 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 3-2 shows the available clock configurations. The ADC clock should be
set according to the MCU operating voltage. Lower operating voltages will require lower ADC clock
frequencies for best accuracy. The analog input level should remain stable for the entire conversion
time (maximum = 17 ADC clock cycles).
Address: $003F
Bit 7
654321
Bit 0
Read:
ADIV2
ADIV1
ADIV0
00000
Write:
Reset:
00000000
= Unimplemented
Figure 3-5. ADC Input Clock Register (ADICLK)
Table 3-2. ADC Clock Divide Ratio
ADIV2
ADIV1
ADIV0
ADC Clock Rate
0
Bus clock ÷ 1
0
1
Bus clock ÷ 2
0
1
0
Bus clock ÷ 4
0
1
Bus clock ÷ 8
1
X
Bus clock ÷ 16
X = don’t care