HD6473258CP10 Datasheet, PDF (25/301 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

Section 2. MCU Operating Modes and Address Space
2.1 Overview
The H8/325 Series operates in three modes numbered 1, 2, and 3. An additional non-operating
mode (mode 0) is used for programming the PROM version of the H8/325. The mode is selected by
the inputs at the mode pins (MD1 and MD0) at the instant when the chip comes out of a reset. As
indicated in table 2-1, the mode determines the size of the address space and the usage of on-chip
ROM and on-chip RAM. The ROMless versions (HD6413258, HD6413238) are used only in
mode 1 (expanded mode with on-chip ROM disabled).
Table 2-1. Operating Modes
MD1 MD0 Mode
Low Low Mode 0
Low High Mode 1
High Low Mode 2
High High Mode 3
Address space
—
Expanded
Expanded
Single-chip
On-chip ROM
—
Disabled
Enabled
Enabled
On-chip RAM
—
Enabled*
Enabled*
Enabled
* 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 64 kbytes.
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 H8/325 Series. Avoid setting the mode pins to mode 0.
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