CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U16898EJ1V0UD
49
Figure 4-4. Block Diagram of P34
RD
P34/RESET
Option
byte
Reset
Internal bus
RD:
Read signal
4.2.3 Port
4
Port 4 is a 6-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 4 (PM4). When the P40 to P45 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 4 (PU4).
Alternate functions include external interrupt request input, serial interface data I/O, and timer output.
Reset input sets port 4 to the input mode.
Figures 4-5 to 4-8 show the block diagrams of port 4.
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