HD64F3437TF16 Datasheet, PDF (86/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

Section 3 MCU Operating Modes and Address Space
3.1 Overview
3.1.1 Mode Selection
The H8/3437 Series operates in three modes numbered 1, 2, and 3. The mode is selected by the
inputs at the mode pins (MD₁ and MD₀). See table 3.1.
Table 3.1 Operating Modes
Mode
MD₁
MD₀
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 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 H8/3437 Series. Avoid setting the mode pins to mode 0, and do not
change the mode pin settings while the chip is operating.
3.1.2 Mode and System Control Registers
Table 3.2 lists the registers related to the chip’s operating mode: the system control register
(SYSCR) and mode control register (MDCR). The mode control register indicates the inputs to the
mode pins MD₁ and MD₀.
Table 3.2 Mode and System Control Registers
Name
System control register
Mode control register
Abbreviation
SYSCR
MDCR
Read/Write
R/W
R
Address
H'FFC4
H'FFC5
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