HD6475348R Datasheet, PDF (44/487 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

Section 2 MCU Operating Modes and Address Space
2.1 Overview
The H8/534 or H8/536 microcomputer unit (MCU) operates in five modes numbered 1, 2, 3, 4,
and 7. The mode is selected by the inputs at the mode pins (MD2 to MD0) at the instant when the
chip comes out of a reset. As indicated in table 2-1, the MCU mode determines the size of the
address space, the usage of on-chip ROM, and the operating mode of the CPU. The MCU mode
also affects the functions of I/O pins.
Table 2-1 Operating Modes
MD2 MD1 MD0
000
001
010
011
100
101
110
111
MCU Mode
—
Mode 1
Mode 2
Mode 3
Mode 4
—
—
Mode 7
Address Space
—
Expanded minimum
Expanded minimum
Expanded maximum
Expanded maximum
—
—
Single-chip only
On-Chip ROM
—
Disabled
Enabled
Disabled
Enabled
—
—
Enabled
CPU Mode
—
Minimum mode
Minimum mode
Maximum mode
Maximum mode
—
—
Minimum mode
Notation: 0: Low level
1: High level
—: Cannot be used
Modes 1 to 4 are referred to as “expanded” because they permit access to off-chip memory and
peripheral addresses. The expanded minimum modes (modes 1 and 2) support a maximum
address space of 64 kbytes. The expanded maximum modes (modes 3 and 4) support a maximum
address space of 1 Mbyte.
Interrupt service is slightly slower in the expanded maximum modes than in the other modes
because the CPU has to save its code page register.
In single-chip mode all ports are available for general-purpose input and output, but off-chip
addresses cannot be accessed.
The H8/534 and H8/536 cannot be set to modes 0, 5, and 6. The mode pins should never be set to
these values.
The inputs at the mode pins must not be changed while the chip is operating.
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