MC68HC05P9A Datasheet, PDF (123/158 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
ADC
I/O Registers
ADRC — ADC RC (Oscillator)
This read/write bit turns on the internal RC oscillator to drive the ADC.
If the internal clock frequency (f_OP) is less than 1 MHz, ADRC must be
set. When the RC oscillator is turned on, it requires a time, t_ADRC, to
stabilize, and results can be inaccurate during this time. Resets clear
the ADRC bit.
1 = Internal RC oscillator drives ADC
0 = Internal clock drives ADC
When the internal RC oscillator is being used as the ADC clock, two
limitations apply:
• Because of the frequency tolerance of the RC oscillator and its
asynchronism with the internal clock, the conversion complete flag
must be used to determine when a conversion sequence is
complete.
• The conversion process runs at the nominal 1.5-MHz rate, but the
conversion results must be transferred to the ADC data register
synchronously with the internal clock; therefore, the conversion
process is limited to a maximum of one channel every internal
clock cycle.
ADON — ADC On
This read/write bit turns on the ADC. When the ADC is on, it requires
a time, t_ADON, for the current sources to stabilize. During this time,
results can be inaccurate. Resets clear the ADON bit.
1 = ADC turned on
0 = ADC turned off
Bits 4 and 3 — Not used
Bits 4 and 3 always read as logic 0s.
11-mc68hc05p9a
MOTOROLA
ADC
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