Section 2. MCU Operating Modes and Address Space
2.1 Overview
2.1.1 Mode Selection
The H8/329 Series operates in three modes numbered 1, 2, and 3. The mode is selected by the
inputs at the mode pins (MD
1
and MD
0
) when the chip comes out of a reset. See table 2-1.
The ROMless versions (HD6413298 and HD6413278) can be used only in mode 1 (expanded mode
with on-chip ROM disabled.)
Table 2-1. Operating Modes
Mode
MD
1
MD
0
Address space
On-chip ROM
On-chip RAM
Mode 0
Low
Low
—
—
—
Mode 1
Low
High
Expanded
Disabled
Enabled*
Mode 2
High
Low
Expanded
Enabled
Enabled*
Mode 3
High
High
Single-chip
Enabled
Enabled
Note: * If the RAME bit in the system control register (SYSCR) is cleared to 0, off-chip memory
can be accessed instead.
Modes 1 and 2 are expanded modes that permit access to off-chip memory and peripheral devices.
The maximum address space supported by these externally expanded modes is 64K bytes.
In mode 3 (single-chip mode), only on-chip ROM and RAM and the on-chip register field are used.
All ports are available for general-purpose input and output.
Mode 0 is inoperative in the H8/329 Series. Avoid setting the mode pins to mode 0.
15
Summary of Contents for H8/326 Series
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