CHAPTER 4 PORT FUNCTIONS
User’s Manual U16899EJ2V0UD
95
4.2.4 Port 3
Port 3 is a 4-bit I/O port with an output latch. Port 3 can be set to the input mode or output mode in 1-bit units
using port mode register 3 (PM3). When used as an input port, use of an on-chip pull-up resistor can be specified in
1-bit units by pull-up resistor option register 3 (PU3).
This port can also be used for external interrupt request input and timer I/O.
RESET input sets port 3 to input mode.
Figures 4-12 and 4-13 show block diagrams of port 3.
Caution In
the
µ
PD78F0138HD, be sure to pull the P31 pin down after reset to prevent malfunction.
Remark P31/INTP2 and P32/INTP3 of the
µ
PD78F0138HD can be used for on-chip debug mode setting when
the on-chip debug function is used. For details, refer to CHAPTER 27 ON-CHIP DEBUG FUNCTION
(
µ
PD78F0138HD ONLY).
Figure 4-12. Block Diagram of P30 to P32
P30/INTP1 to
P32/INTP3
WR
PU
RD
WR
PORT
WR
PM
PU30 to PU32
Alternate
function
Output latch
(P30 to P32)
PM30 to PM32
EV
DD
P-ch
Selector
Internal bus
PU3
PM3
PU3:
Pull-up resistor option register 3
PM3:
Port mode register 3
RD: Read
signal
WR
××
: Write
signal