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3.1
Overview
3.1.1
Operating Mode Selection
The H8S/2633 Series has four operating modes (modes 4 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 3-1 lists the MCU operating modes.
Table 3-1
MCU Operating Mode Selection
MCU
Operating
Mode
MD2 MD1 MD0
0*
0
0
1*
2*
1
3*
4
1
0
5
6
1
7
Note: * Not available in the H8S/2633 Series.
The CPU's architecture allows for 4 Gbytes of address space, but the H8S/2633 Series actually
accesses a maximum of 16 Mbytes.
Modes 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.
Section 3 MCU Operating Modes
CPU
Operating
Mode
0
—
1
—
0
1
0
Advanced On-chip ROM disabled,
1
0
1
Description
—
expanded mode
On-chip ROM enabled,
expanded mode
Single-chip mode
External Data Bus
On-Chip
Initial
ROM
Width
—
—
Disabled 16 bits
8 bits
Enabled 8 bits
—
Max.
Width
16 bits
16 bits
16 bits
67
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