Port 3 - NEC 78K0 User Manual

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 by
pull-up resistor option register 3 (PU3).
This port can also be used for external interrupt request input.
RESET input sets port 3 to input mode.
Figures 4-12 and 4-13 show block diagrams of port 3.
WR
PU
RD
WR
PORT
WR
PM
PU3: Pull-up resistor option register 3
PM3: Port mode register 3
RD: Read signal
WR××: Write signal
CHAPTER 4 PORT FUNCTIONS
Figure 4-12. Block Diagram of P30 to P32
PU3
PU30 to PU32
Alternate
function
Output latch
(P30 to P32)
PM3
PM30 to PM32
User's Manual U15947EJ2V0UD
*
EV
DD
P-ch
P30/INTP1 to
P32/INTP3
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