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CHAPTER 4 PORT FUNCTIONS
User’s Manual U15104EJ2V0UD
Figure 4-9. Block Diagram of Key Input Detector
WR
PM
WR
PORT
RD
Selector
Output latch
(P50 to P57)
PM50 to PM57
Internal bus
P50 to P57
P40
P41
P42
P43
P44
P45
P46
P47
INTKR
Key input
detector
“1” when MEM = 01H
Cautions 1. This register is valid only when the MEM register is set to 01H.
2. Key return can be detected only when all the pins of P40 to P47 are high level.
When any one is low level, even if falling edge is generated at the other pins, the key return
signal cannot be detected.
4.2.5 Port 5
Port 5 is an 8-bit I/O port with an output latch. Input or output mode can be specified for port 5 in 1-bit units using
port mode register 5 (PM5).
Reset input sets port 5 to the input mode.
Figure 4-10 shows the block diagram of port 5.
Figure 4-10. Block Diagram of P50 to P57
PM:
Port mode register
RD:
Port 5 read signal
WR: Port 5 write signal
Содержание mPD178053
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