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CHAPTER 19 EXTERNAL DEVICE EXPANSION FUNCTION
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CHAPTER 19 EXTERNAL DEVICE EXPANSION FUNCTION
19.1 External Device Expansion Functions
The external device expansion functions are intended to connect external devices to areas other than the internal
ROM, RAM and SFR. Connection of external devices uses port 4 to port 6. Port 4 to port 6 control address/data,
read/write strobe, wait, address strobe, etc.
Table 19-1. Pin Functions in External Memory Expansion Mode
Pin Function at External Device Connection
Alternate
Name
Function
Function
AD0 to AD7
Multiplexed address/data bus
P40 to P47
A8 to A15
Address bus
P50 to P57
RD
Read strobe signal
P64
WR
Write strobe signal
P65
WAIT
Wait signal
P66
ASTB
Address strobe signal
P67
Table 19-2. State of Port 4 to Port 6 Pins in External Memory Expansion Mode
Port
Port 4
Port 5
Port 6
External
0 to 7
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
Expansion Mode
Single-chip mode
Port
Port
Port
256 bytes expansion
Address/Data
Port
Port
RD, WR, WAIT, ASTB
mode
4 Kbytes expansion
Address/Data
Address
Port
Port
RD, WR, WAIT, ASTB
mode
16 Kbytes expansion
Address/Data
Address
Port
Port
RD, WR, WAIT, ASTB
mode
Full-address mode
Address/Data
Address
Port
RD, WR, WAIT, ASTB
Caution
When the external wait function is not used, the WAIT pin can be used as a port in all modes.
Summary of Contents for 78014Y Series
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