UPD78F9234MC-5A4-A Datasheet, PDF (59/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 4 PORT FUNCTIONS
4.2.3 Port 3
Pins P30 to P33 constitute a 4-bit I/O port with an output latch. Each bit of this port can be set to the input or
output mode by using port mode register 3 (PM3). When the P30 to P33 pins are used as an input port, an on-chip
pull-up resistor can be connected in 1-bit units by using pull-up resistor option register 3 (PU3).
The P30 and P31 pins are also used for both timer I/O and external interrupt request input pin functions.
Generation of reset signal sets port 3 to the input mode.
P34 is a 1-bit input-only port. This pin is also used as a RESET pin, and when the power is turned on, this is the
reset function.
For settings of alternate function, refer to CHAPTER 18 OPTION BYTE. When using P34 as input port, pull up the
P34 pin by using external resistor.
Figures 4-4 to 4-7 show the block diagrams of port 3.
WRPU
RD
Figure 4-4. Block Diagram of P30
PU3
PU30
Alternate
function
VDD
P-ch
WRPORT
WRPM
P3
Output latch
(P30)
PM3
PM30
P30/TI000/INTP0
PU3: Pull-up resistor option register 3
P3: Port register 3
PM3: Port mode register 3
RD: Read signal
WR××: Write signal
User’s Manual U17446EJ5V0UD
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