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Section 3 MCU Operating Modes
3.1 Overview
3.1.1 Operating Mode Selection
The H8/3035 Series has three operating modes (modes 1 to 3) that are selected by the mode pins
(MD
and MD
) as indicated in table 3-1. The input at these pins determines expanded mode or
1
0
single-chip mode.
Table 3-1 Operating Mode Selection
Operating Mode MD
1
—
0
Mode 1
0
Mode 2
1
Mode 3
1
Notes: 1. In modes 1 and 2, if the RAM enable bit (RAME) in the system control register
(SYSCR) is cleared to 0, these addresses become external addresses.
2. In mode 3, clearing bit RAME of SYSCR to 0 and reading the on-chip RAM always
returns H'FF, and write access is ignored. For details, see section 13.3, Operation.
For the address space size there is a choice of 1 Mbyte or 16 Mbytes.
Modes 1 and 3 support a maximum address space of 1 Mbyte. Mode 2 supports a maximum
address space of 16 Mbytes.
The H8/3035 Series can only be used in mode 1, 2, or 3. The inputs at the mode pins must
select one of these three modes. The inputs at the mode pins must not be changed during
operation.
3.1.2 Register Configuration
The H8/3035 Series has a mode control register (MDCR) that indicates the inputs at the mode
pins (MD
and MD
), and a system control register (SYSCR). Table 3-2 summarizes these
1
0
registers.
Mode Pins
MD
Address Space Initial Bus Width On-Chip RAM
0
0
—
1
1 Mbyte
0
16 Mbytes
1
1 Mbyte
Description
—
—
8 bits
Enabled
8 bits
Enabled
—
Enabled
*1
*1
*2
53
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