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CONNECTION WITH EXTERNAL DEVICES
(1) External bus (A
External areas are specified by the address (A
Pins A
to A
of the external address bus and pins D
8
23
to the same pins. When the BYTE pin level, described later, is "L" (i.e., external data bus width is
16 bits), the A
8
with time-sharing. When the BYTE pin level is "H" (i.e., external data bus width is 8 bits), the
A
/D
to A
/D
16
0
23
7
A
output addresses.
15
000000
000080
000880
004000
010000
FFFFFF
Note: Addresses 2
Fig. 12.1.2 External area
12.1 Signals required for accessing external devices
to A
, A
/D
to A
0
7
8
8
15
/D
to A
/D
and A
/D
8
15
15
16
pins perform address output and data input/output with time-sharing, and pins A
Memory expansion mode
16
SFR area
(Note)
16
Internal RAM
area
16
16
Internal ROM
area
16
16
: External area
to 9
become an external area.
16
16
7751 Group User's Manual
/D
, A
/D
to A
/D
)
15
16
0
23
7
to A
) output. Figure 12.1.2 shows the external area.
0
23
to D
0
to A
/D
pins perform address output and data input/output
0
23
7
000000
000080
000880
FFFFFF
of the external data bus are assigned
15
Microprocessor mode
16
SFR area
(Note)
16
Internal RAM
area
16
16
to
8
12–5
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