HD404639R Datasheet, PDF (107/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

HD404639R Series
command. Only bit CER3 corresponds to the analog input pin selected with bits CER0 and CER1. After a
compare operation, the data in this register is not retained.
Note on Use: During the compare operation pins RD₀/COMP₀–RD₃/COMP₃ operate as analog inputs and
cannot operate as R ports.
The comparator can operate in active mode and subactive mode but is disabled in other modes.
The switch for the internal reference voltage is on only when the internal reference voltage is selected by
CER2.
RE₀/VC_ref cannot operate as an R port when the external input voltage is selected as the reference.
Compare enable register (CER: $018)
Bit
Initial value
Read/Write
Bit name
3
0
W
CER3
2
0
W
CER2
1
0
W
CER1
0
0
W
CER0
CER3 Digital/Analog selection
0 Digital input mode:
RD₀ /COMP₀–RD₃ /COMP₃
operate as R port
1 Analog input mode:
RD₀ /COMP₀–RD₃ /COMP₃
operate as analog input
CER1
0
1
CER0 Analog input pin selection
0 COMP₀
1 COMP₁
0 COMP₂
1 ^COMP3
CER2
0
1
Reference voltage selection
External input voltage
Internal voltage
Figure 90 Compare Enable Register (CER)
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