MC68HC705P6A Datasheet, PDF (81/130 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Analog Subsystem
A/D Status and Control Register (ADSC)
obtained. See 9.3.2 Reference Voltage (VREFH) for more
information.
ADON — A/D Subsystem On
When the A/D subsystem is turned on (ADON = 1), it requires a time,
t_ADON, to stabilize before accurate conversion results can be attained.
CH2–CH0 — Channel Select Bits
CH2, CH1, and CH0 form a 3-bit field which is used to select an input
to the A/D converter. Channels 0–3 correspond to port C input pins
PC6–PC3. Channels 4–6 are used for reference measurements.
Channel 7 is reserved. If a conversion is attempted with channel 7
selected, the result will be $00. Table 9-1 lists the inputs selected by
bits CH0-CH3.
If the ADON bit is set and an input from channels 0–4 is selected, the
corresponding port C pin’s DDR bit will be cleared (making that port
C pin an input). If the port C data register is read while the A/D is on
and one of the shared input channels is selected using bit CH0–CH2,
the corresponding port C pin will read as a logic 0. The remaining port
C pins will read normally. To digitally read a port C pin, the A/D
subsystem must be disabled (ADON = 0), or input channels 5–7 must
be selected.
Table 9-1. A/D Multiplexer Input
Channel Assignments
Channel
0
1
2
3
4
5
6
7
Signal
AD0 — port C, bit 6
AD1 — port C, bit 5
AD2 — port C, bit 4
AD3 — port C, bit 3
V_REFH — port C, bit 7
(V_REFH + V_SS)/2
V_SS
Reserved for factory test
MC68HC705P6A — Rev. 2.0
MOTOROLA
Analog Subsystem
Advance Information
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