MagnaChip MC80C0104, User Manual, Page: 40 / 126

MC80F0104/0204 Preliminary
36 Mar. 2005 Ver 0.2
9.3 R3 and R3IO register
R3 is a 5-bit CMOS bidirectional I/O port (address 0C6
H
).
Each I/O pin (except R35) can independently used as an in-
put or an output through the R3IO register (address 0C7
H
).
R35 is an input only port. When R31 through R35 pins are
used as input ports, an on-chip pull-up resistor can be con-
nected to them in 1-bit units with a pull-up selection regis-
ter 3 (PU3). R31 through R34 pins can be used to open
drain output port by setting the corresponding bit of the
open drain selection register 3 (R3OD).
In addition, Port R3 is multiplexed with alternate func-
tions. R31 and R32 can be used as ADC input channel 14
and 15 by setting ADCM to enable ADC and select chan-
nel 14 and 15.
R33, R34 and R35 is multiplexed with X
IN
, X
OUT
, and
RESET pin. These pins can be used as general I/O pins by
setting writing option described in "23. Device Configura-
tion Area" on page 102.
Port Pin Alternate Function
R31
R32 AN14 (ADC input channel 14)
AN15 (ADC input channel 15)
R3 Data Register
R3
ADDRESS: 0C6
H
RESET VALUE: --00 000-
B
- - R35 R34 R33 R32 R31 -
Port Direction
R3 Direction Register
R3IO
ADDRESS: 0C7
H
RESET VALUE: ---0 000-
B
0: Input
1: Output
Input / Output data
- - -
Input data
-
R3 Pull-up
PU3
ADDRESS: 0FF
H
RESET VALUE: --00 000-
B
Selection Register
0: Disable
1: Enable
Pull-up Resister Selection
- -
R3 Open Drain
R3OD
ADDRESS: 0CB
H
RESET VALUE: ---0 000-
B
Selection Register
0: Disable
1: Enable
Open Drain Resister Selection
-