Port 4 - NEC 78K0R/KE3 User Manual

4.2.5 Port 4

Port 4 is a 4-bit I/O port with a output latch. Port 4 can be set to the input mode or output mode in 1-bit units using
port mode register 4 (PM4). When the P40 to P43 pins are 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 4 (PU4)
This port can also be used for flash memory programmer/debugger data I/O, clock output, and timer I/O.
Reset signal generation sets port 4 to input mode.
Figures 4-14 to 4-17 show block diagrams of port 4.
Note When a tool is connected, the P40 and P41 pins cannot be connected to a pull-up resistor.
Cautions 1. When a tool is connected, the P40 pin cannot be used as a port pin.
When the on-chip debug function is used, P41 pin can be used as follows by the mode setting
on the debugger.
1-line mode: can be used as a port (P41).
2-line mode: used as a TOOL1 pin and cannot be used as a port (P41).
2. To use P42/TI04/TO04 as a general-purpose port, set bit 4 (TO04) of timer output register 0
(TO0) and bit 4 (TOE04) of timer output enable register 0 (TOE0) to "0", which is the same as
their default status setting.
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CHAPTER 4 PORT FUNCTIONS
User's Manual U17854EJ9V0UD
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