Freescale Semiconductor, Inc.
Analog Subsystem
A/D Conversion Methods
tDIS
tDIS
tDIS
(MIN)
(MIN)
V
CAP
VMAX
tCHG
tCHG x ICHG
V
V =
X
X
CEXT
CHG
COMP2
TOF
OCF
ICF
0
1
2
3
1
2
Point
Action
Software/Hardware Action
Dependent Variable(s)
Begin initial discharge and select
mode 1 by clearing CHG and
ATD2 and setting ATD1 in the
ACR.
0
Software write
Software
1
2
V
falls to V
.
Wait out minimum t
time
V
, I , C
MAX DIS EXT
CAP
SS
DIS
Stop discharge and begin charge by
setting CHG control bit in ACR.
Software write
Software
V
rises to V and comparator 2
X
CAP
output trips, setting CPF2 and
CMP2, which clears CHG control
bit in the ACR. Reset CPF2 by
writing a “1” to CPFR2.
Wait out t
CPF2 clears CHG control bit
time.
CHG
3
V , I
, C
CHG EXT
X
Figure 8-9. A/D Conversion — Manual/Auto Discharge Control (Mode 1)
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
General Release Specification
Analog Subsystem
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