Motorola 68HC12 User Manual page 9

Table 2: Prescalar Values
Prescale Value
00000
00001
00010
00011
00100
00101
00110
00111
01xxx
1xxxx
_H12ADTCTL5 is used to select the conversion mode, which channels are to be
converted and to initiate the conversions.
any write made to this register.
conversion sequence is in progress, the conversion is aborted and the SCF and CCF
flags are reset.
_H12ADTCTL5:
bit 7 bit 6
unused S8CM
S8CM is used to select between making 4 conversions, when the bit is set to zero,
and 8 conversions, when the bit is set to one.
SCAN is used to select between performing either a single conversion or multiple
conversions. If SCAN is set to zero, then a single conversion will be run and the
flag will then be set.
continuous conversions on the A/D channels.
MULT determines whether the conversion is run on a single channel or on multiple
channels. When MULT zero, the A/D converter runs all the conversions on a single
channel, which is selected by CD,CC,CB, and CA.
is run on several different channels in the group specified by CD,CC,CB, and CA.
The possible channel combinations are in Table 3.
Table 3: A/D Converter Settings
S8CM CD CC CB
0 0 0 0*
0 0 0 0*
0 0 0 1*
0 0 0 1*
0 0 1 0*
0 0 1 0*
0 0 1 1*
0 0 1 1*
0 1 0 0*
0 1 0 0*
0 1 0 1*
0 1 0 1*
0 1 1 0*
0 1 1 0*
0 1 1 1*
0 1 1 1*
1 0 0* 0*
1 0 0* 0*
1 0 0* 1*
Divisor___
Do not use
/4
/6
/8
/10
/12
/14
/16
Do not use
Do not use
If a write is made to this register while a
bit 5 bit 4
SCAN MULT
If SCAN is set to 1, then the A/D converter will run
CA Channel Signal
0* AN0
1* AN1
0* AN2
1* AN3
0* AN4
1* AN5
0* AN6
1* AN7
0* Reserved
1* Reserved
0* Reserved
1* Reserved
0* V RH
1* V RL
0* (V RH + V RL )/2
1* TEST/Reserved
0* AN0
1* AN1
0* AN2
The conversion sequence is started by
bit 3 bit 2
CD CC
When MULT is one, the conversion
Result in ADRx if MULT = 1
ADR0
ADR1
ADR2
ADR3
ADR0
ADR1
ADR2
ADR3
ADR0
ADR1
ADR2
ADR3
ADR0
ADR1
ADR2
ADR3
ADR0
ADR1
ADR2
9
bit 1 bit 0
CB CA