Section 3 Mcu Operating Modes; Overview; Operating Mode Selection - Hitachi H8/3008 Hardware Manual

3.1

Overview

3.1.1

Operating Mode Selection

The H8/3008 has four operating modes (modes 1 to 4) that are selected by the mode pins (MD
MD ) as indicated in table 3.1. The input at these pins determines the size of the address space and
0
the initial bus mode.
Table 3.1 Operating Mode Selection
Mode Pins
Operating
Mode MD
2
— 0
Mode 1 0
Mode 2 0
Mode 3 0
Mode 4 1
— 1
— 1
— 1
Notes: 1. In modes 1 to 4, an 8-bit or 16-bit data bus can be selected on a per-area basis by
settings made in the area bus width control register (ABWCR). For details see
section 6, Bus Controller.
2. If the RAME bit in SYSCR is cleared to 0, these addresses become external addresses.
For the address space size there are three choices: 1 Mbyte or 16 Mbyte. The external data bus is
either 8 or 16 bits wide depending on ABWCR settings. 8-bit bus mode is used only if 8-bit access
is selected for all areas. For details see section 6, Bus Controller.

Section 3 MCU Operating Modes

Address
MD MD Space
1 0
0 0 Setting
prohibited
0 1 Expanded
mode
1 0 Expanded
mode
1 1 Expanded
mode
0 0 Expanded
mode
0 1 Setting
prohibited
1 0 Setting
prohibited
1 1 Setting
prohibited
Description
Initial Bus On-Chip
1
Mode* ROM
Setting Setting
prohibited prohibited
8 bits Disabled
16 bits Disabled
8 bits Disabled
16 bits Disabled
Setting Setting
prohibited prohibited
Setting Setting
prohibited prohibited
Setting Setting
prohibited prohibited
to
2
On-Chip
RAM
Setting
prohibited
2
Enabled*
2
Enabled*
2
Enabled*
2
Enabled*
Setting
prohibited
Setting
prohibited
Setting
prohibited
55