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MC68HC05JJ6 Datasheet, PDF (127/216 Pages) Freescale Semiconductor, Inc – General Release Specification Microcontrollers
VCAP
VX
tDIS
tDIS
(MIN)
Analog Subsystem
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
Begin initial discharge and select mode
3 by clearing CHG and setting ATD2
and ATD1 in the ACR. Also set ICEN
bit in ACR and IEDG bit in TCR.
VCAP falls to VSS. Set timer output
compare registers (OCRH and OCRL)
to desired charge start time.
Stop discharge and begin charge when
the next OCF sets the CHG control bit
in ACR.
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. Load next OCF.
Software/Hardware Action
Software write
Wait out minimum tDIS time.
Software write to OCRH, OCRL
Timer OCF sets the CHG control
bit in the ACR.
Wait out tCHG time.
Timer ICF clears the CHG
control bit in the ACR.
Dependent Variable(s)
Software
VMAX, IDIS, CEXT,
software
Free-running timer
output compare, fOSC
VX, ICHG, CEXT
Figure 8-11. A/D Conversion — OCF/ICF Control (Mode 3)
MC68HC05JJ6/MC68HC05JP6 — Rev. 3.2
Freescale Semiconductor
Analog Subsystem
General Release Specification
127