NEC mPD780852 Series, Preliminary User'S Manual

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CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U14581EJ3V0UM00
4.2.6 Port 5
Port 5 is a 5-bit input/output port with output latch. P50 to P54 pins can specify the input mode/output mode in
1-bit units with the port mode register 5 (PM5).
Alternate functions include serial interface data input/output and clock input/output.
RESET input sets port 5 to input mode.
Figure 4-7 shows a block diagram of port 5.
Caution When port 0 is used as the serial interface pins, an I/O and output latches must be set according
to the functions to be used. For an explanation of how to set these latches, refer to the
description of the format of the serial operation mode register.
Figure 4-7. P50 to P54 Block Diagram
RD
P50/SCK3
P51/SO3
P52/SI3
P53/RxD
P54/TxD
WR
PORT
WR
PM
Output latch
(P50 to P54)
PM50 to PM54
Alternate
functions
Selector
Internal bus
PM: Port mode register
RD: Port 5 read signal
WR: Port 5 write signal