Chapter 22 External Device Expansion Function; External Device Expansion Functions; Pin Functions In External Memory Expansion Mode; State Of Ports 4 To 6 Pins In External Memory Expansion Mode - NEC PD78052 User Manual

CHAPTER 22 EXTERNAL DEVICE EXPANSION FUNCTION

22.1 External Device Expansion Functions

The external device expansion functions connect external devices to areas other than the internal ROM, RAM,
and SFR. Connection of external devices uses ports 4 to 6. Ports 4 to 6 control address/data, read/write strobe,
wait, address strobe etc.
Table 22-1. Pin Functions in External Memory Expansion Mode
Pin function at external device connection
Name
AD0 to AD7
A8 to A15
RD
WR
WAIT
ASTB
Table 22-2. State of Ports 4 to 6 Pins in External Memory Expansion Mode
Ports and bits
Modes
Single-chip mode
256-byte expansion mode
4K-byte expansion mode
16K-byte expansion mode
Full address mode
Caution When the external wait function is not used, the WAIT pin can be used as a port in all modes.
Function
Multiplexed address/data bus
Address bus
Read strobe signal
Write strobe signal
Wait signal
Address strobe signal
Port 4
0-7 0 1 2 3 4 5 6 7
Port
Address/data
Address/data Address
Address/data
Address/data
Alternate function
P40 to P47
P50 to P57
P64
P65
P66
P67
Port 5
0-3
Port Port
Port Port
Port Port
Address Port Port
Address Port
Port 6
4-7
Port
RD, WR, WAIT, ASTB
RD, WR, WAIT, ASTB
RD, WR, WAIT, ASTB
RD, WR, WAIT, ASTB
511