h8s-2646 Renesas Electronics Corporation., h8s-2646 Datasheet - Page 103

• Manufacturer Part Number: h8s-2646
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

3.1
3.1.1
The H8S/2646 Group 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
Note: * Not available in the H8S/2646 Group.
The CPU’s architecture allows for 4 Gbytes of address space, but the H8S/2646 Group 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.
MCU
Operating
Mode
0 *
1 *
2 *
3 *
4
5
6
7
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
Description
—
On-chip ROM disabled,
expanded mode
On-chip ROM enabled,
expanded mode
Single-chip mode
Rev. 5.00 Sep 22, 2005 page 77 of 1136
Section 3 MCU Operating Modes
On-Chip
ROM
—
Disabled 16 bits
Enabled 8 bits
Initial
Width
—
8 bits
—
External Data Bus
REJ09B0257-0500
Max.
Width
—
16 bits
16 bits
16 bits
—