XC68HC05P18A Motorola, XC68HC05P18A Datasheet - Page 95

• Manufacturer Part Number: XC68HC05P18A
• Description: HCMOS Microcontroller Unit
• Manufacturer: Motorola

MC68HC05P18A
MOTOROLA
R — Reserved Bit
ADON — A/D Subsystem On Bit
CH2–CH0 — Channel Select Bits
This bit is not currently used. It can be read or written, but does not
control anything.
When the A/D subsystem is turned on (ADON = 1), it requires a time
t
CH2, CH1, and CH0 form a 3-bit field that 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. In
user mode, channel 7 is reserved. If a conversion is attempted with
channel 7 selected, the result is $00.
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 is 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 reads as a logic 0. The remaining port C pins
read normally. To digitally read a port C pin, the A/D subsystem must
be disabled (ADON = 0) or input channel 5–7 must be selected.
ADON
to stabilize before accurate conversion results can be attained.
Analog-to-Digital (A/D) Converter
Channel
0
1
2
3
4
5
6
7
Table 11-1. A/D Multiplexer Input
Channel Assignments
V
AD0 port C bit 6
AD1 port C bit 5
AD2 port C bit 4
AD3 port C bit 3
(V
REFH
Table 11-1
REFH
Reserved
Signal
Analog-to-Digital (A/D) Converter
port C bit 7
V
A/D Status and Control Register
SS
+ V
SS
)/2
lists the inputs
Technical Data
95