HD6432351 Datasheet, PDF (90/989 Pages) Renesas Technology Corp – The H8S/2000 CPU has an internal 32-bit architecture, is provided with sixteen 16-bit general registers and a concise

The H8S/2350 can be used only in modes 1, 4, and 5. This means that the mode pins must be set
to select one of these modes. Do not change the inputs at the mode pins during operation.
3.1.2 H8S/2351 Operating Mode Selection
The H8S/2351 has seven operating modes (modes 1 to 7). These modes enable selection of the
CPU operating mode, enabling/disabling of on-chip ROM, and the initial bus width setting, by
setting the mode pins (MD₂ to MD₀).
Table 3-2 lists the MCU operating modes.
Table 3-2 MCU Operating Mode Selection (H8S/2351)
MCU
CPU
Operating
Operating
Mode
MD₂ MD₁ MD₀ Mode
Description
0
000—
—
External Data Bus
On-Chip Initial
ROM Width
Max.
Width
—
—
1
1 Normal On-chip ROM disabled, Disabled 8 bits
16 bits
expanded mode
2
10
On-chip ROM enabled, Enabled 8 bits
16 bits
expanded mode
3
1
Single-chip mode
—
4
1 0 0 Advanced On-chip ROM disabled, Disabled 16 bits 16 bits
5
1
expanded mode
8 bits
16 bits
6
10
On-chip ROM enabled, Enabled 8 bits
16 bits
expanded mode
7
1
Single-chip mode
—
The CPU's architecture allows for 4 Gbytes of address space, but the H8S/2351 actually accesses a
maximum of 16 Mbytes.
Modes 1, 2, and 4 to 6 are externally expanded modes that allow access to external memory and
peripheral devices.
The external expansion modes allow switching between 8-bit and 16-bit bus modes. After program
execution starts, an 8-bit or 16-bit address space can be set for each area, depending on the bus
controller setting. If 16-bit access is selected for any one area, 16-bit bus mode is set; if 8-bit
access is selected for all areas, 8-bit bus mode is set.
Note that the functions of each pin depend on the operating mode.
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