MC68HC705P9CDW FREESCALE [Freescale Semiconductor, Inc], MC68HC705P9CDW Datasheet - Page 135

• Manufacturer Part Number: MC68HC705P9CDW
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

MC68HC705P9 — Rev. 4.0
MOTOROLA
When the internal RC oscillator is being used as the ADC clock, two
limitations apply:
ADON — ADC On
Bits 4–2 — Not used
CH[2:0] — Channel Select Bits
•
•
This read/write bit turns on the ADC. When the ADC is on, it requires
a time, t
results can be inaccurate. Resets clear the ADON bit.
Bits 4–2 always read as logic zeros.
These read/write bits select one of eight ADC input channels as
shown in
PC4/AN2, PC5/AN1, and PC6/AN0. Channels 4–6 can be used for
reference measurements. Channel 7 is reserved for factory testing.
Freescale Semiconductor, Inc.
For More Information On This Product,
1 = ADC turned on
0 = ADC turned off
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.
Analog-to-Digital Converter (ADC)
ADON
Table
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Table 11-2. ADC Input Channel Selection
, for the current sources to stabilize. During this time,
CH[2:1:0]
000
001
010
011
100
101
110
111
11-2. Channels 0–3 are the input pins, PC3/AN3,
Channel
0
1
2
3
4
5
6
7
(V
Analog-to-Digital Converter (ADC)
RH
Reserved
Signal
AN0
AN1
AN2
AN3
+ V
V
V
RH
SS
SS
) / 2
Technical Data
I/O Registers
135