HD6432646 Hitachi, HD6432646 Datasheet - Page 113

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

3.1
3.1.1
The H8S/2646 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
0*
1*
2*
3*
4
5
6
7
Note: * Not available in the H8S/2646 Series.
The CPU’s architecture allows for 4 Gbytes of address space, but the H8S/2646 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.
Overview
Operating Mode Selection
MD2 MD1 MD0
0
1
MCU Operating Mode Selection
0
1
0
1
Section 3 MCU Operating Modes
0
1
0
1
0
1
0
1
CPU
Operating
Mode
—
—
Advanced On-chip ROM disabled,
Description
—
expanded mode
On-chip ROM enabled,
expanded mode
Single-chip mode
On-Chip
ROM
—
Disabled 16 bits
Enabled
External Data Bus
Initial
Width
—
8 bits
8 bits
—
Max.
Width
—
16 bits
16 bits
16 bits
—
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