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CHAPTER 4 PORT FUNCTIONS
User’s Manual U15104EJ2V0UD
4.2.3 Port 3
Port 3 is an 8-bit I/O port with an output latch. Input or output mode can be specified for port 3 in 1-bit units using
port mode register 3 (PM3).
Alternate functions include timer input and buzzer output.
Reset input sets port 3 to the input mode.
Figures 4-5 to 4-7 show the block diagrams of port 3.
Figure 4-5. Block Diagram of P30 to P32 and P35
PM:
Port mode register
RD:
Port 3 read signal
WR: Port 3 write signal
RD
P30 to P32, P35
WR
PORT
WR
MM
Output latch
(P30 to P32, P35)
PM30 to PM32,
PM35
Selector
Internal bus