
I-18
EPSON
S1C88348/317/316/308 TECHNICAL HARDWARE
3 CPU AND BUS CONFIGURATION
Since there is no need for an external bus line in
this mode, terminals normally set for bus use
can be used as general purpose output ports or
I/O ports.
Accordingly, the output ports are in a 34-bit
configuration in the S1C88348/317/316 and 30-
bit in the S1C88308. The I/O ports are in a 16-bit
configuration in both the models.
CPU operation in this mode is equivalent to the
S1C88 core CPU Model 3 minimum mode.
Addresses assigned to internal memory within
physical space 000000H to 00FFFFH are only
effective as a target for accessing.
s Expanded 64K mode
The expanded 64K mode setting applies when
the S1C883xx is used with 64K bytes or less of
external expanded memory. In the S1C88316/
308, this mode is usable regardless of the MCU/
MPU mode setting. In the S1C88348/317, it can
be used only in the MPU mode.
Because internal ROM is being used in the MCU
mode, external memory in that area is not
accessible.
External memory can be assigned to the area
from 004000H to 00EFFFH in the S1C88348/
317/316 and to the area from 002000H to
00EFFFH in the S1C88308.
Since the internal ROM area is released in the
MPU mode, external memory can be assigned
to the area from 000000H to 00EFFFH. The area
from 00F000H to 00FFFFH is assigned to
internal memory (RAM, etc.) and cannot be
used to access an external device.
This mode setting is suitable for small- to mid-
scale systems. The address range of the chip
enable (CE) signal, adapted to memory chips
with a capacity of from 8 to 64K bytes, can be
selected in software to any one of four settings.
See Section 3.6.4, "Chip enable (CE) signal", for
the CE signal.
CPU operation in this mode is equivalent to the
S1C88 core CPU Model 3 minimum mode. The
area within physical space 000000H to 00FFFFH
is only effective as a target for accessing.
The S1C88348 and S1C88317 do not support the expanded 64K + MCU mode.
Fig. 3.5.2.2 Memory map for the expanded 64K mode
S1C88308
S1C88348/317/
316/308
- MCU mode -
00FFFFH
00F000H
00EFFFH
:
004000H
003FFFH
002000H
001FFFH
000000H
Internal memory
External
memory area
Internal memory
S1C88316
- MCU mode -
See Figure 3.2.1 for the internal memory
- MPU mode -
Internal memory
External
memory area
Internal memory
External
memory area