Port 5 - NEC 78K0 User Manual

4.2.6

Port 5

Port 5 is an 8-bit I/O port with an output latch. Port 5 can be set to the input mode or output mode in 1-bit units
using port mode register 5 (PM5). Use of an on-chip pull-up resistor can be specified in 1-bit units using pull-up
resistor option register 5 (PU5).
This port can also be used as an address bus in external memory expansion mode.
RESET input sets port 5 to input mode.
Figure 4-15 shows a block diagram of port 5.
WR
PU
RD
WR
PORT
WR
PM
Memory expansion
PU5: Pull-up resistor option register 5
PM5: Port mode register 5
RD: Read signal
WR××: Write signal
112
CHAPTER 4 PORT FUNCTIONS
Figure 4-15. Block Diagram of P50 to P57
PU5
PU50 to PU57
Selector
Output latch
(P50 to P57)
Selector
Alternate
function
PM5
PM50 to PM57
mode register
(MEM)
User's Manual U15947EJ2V0UD
EV
DD
P-ch
*
P50/A8 to P57/A15