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MC68HC705JJ7 Datasheet, PDF (87/164 Pages) Freescale Semiconductor, Inc – Microcontrollers
VCAP
VX
tDIS
tDIS
(MIN)
A/D Conversion Methods
tDIS
(MIN)
VMAX
tCHG
VX = tCHG x ICHG
CEXT
CHG
COMP2
(TCAP)
TOF
OCF
ICF
0
1
2
31
2
Point
0
1
2
3
Action
Software/Hardware Action
Dependent Variable(s)
Begin initial discharge and select mode 2 by
clearing CHG and ATD1 and setting ATD2 in
the ACR. Also set ICEN bit in ACR and IEDG
bit in TCR.
Software write
Software
VCAP falls to VSS.
Wait out minimum tDIS time.
VMAX, IDIS, CEXT
Stop discharge and begin charge when the
next TOF sets the CHG control bit in ACR.
Timer TOF sets the CHG control bit in Free-running timer counter
the ACR.
overflow, fOSC
VCAP rises to VX and comparator 2 output
trips, setting CPF2 and CMP2, which causes
an ICF from the timer and clears the CHG
control bit in ACR. Must clear CPF2 to trap
next CPF2 flag.
Wait out tCHG time.
Timer ICF clears the CHG control bit
in the ACR.
VX, ICHG, CEXT
Figure 8-10. A/D Conversion — TOF/ICF Control (Mode 2)
MC68HC705JJ7 • MC68HC705JP7 Advance Information Data Sheet, Rev. 4.1
Freescale Semiconductor
87