Port 12 - NEC mPD178054 Series User Manual

4.2.8 Port 12

Port 12 is a 6-bit I/O port with an output latch. Input or output mode can be specified for port 12 in 1-bit units using
port mode register 12 (PM12).
Alternate functions include serial interface data I/O and clock I/O.
Reset input sets port 12 to the input mode.
Figures 4-16 to 4-18 show the block diagrams of port 12.
RD
WR
PORT
WR
PM
PM: Port mode register
RD: Port 12 read signal
WR: Port 12 write signal
80
CHAPTER 4 PORT FUNCTIONS
Figure 4-16. Block Diagram of P120 and P123
Alternate function
Output latch
(P120, P123)
PM120, PM123
User's Manual U15104EJ2V0UD
P120/SI32
P123/SI321