HD64F2149 Datasheet, PDF (693/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

Bits 6 to 2—Reserved: These bits cannot be modified and are always read as 0.
Bits 1 and 0—Mode Select 1 and 0 (MDS1, MDS0): These bits indicate values that reflects the
input levels of mode pins MD1 and MD0 (the current operating mode). Bits MDS1 and MDS0
correspond to pins MD1 and MD0, respectively. These are read-only bits, and cannot be modified.
When MDCR is read, the input levels of mode pins MD1 and MD0 are latched in these bits.
22.3 Operation
The on-chip ROM is connected to the CPU by a 16-bit data bus, and both byte and word data is
accessed in one state. Even addresses are connected to the upper 8 bits, and odd addresses to the
lower 8 bits. Word data must start at an even address.
The mode pins (MD1 and MD0) and the EXPE bit in MDCR can be set to enable or disable the
on-chip ROM, as shown in table 22.2.
In normal mode, the maximum amount of ROM that can be used is 56 kbytes.
Table 22.2 Operating Modes and ROM
Operating Mode
MCU
CPU
Operating Operating
Mode
Mode
Mode 1 Normal
Mode 2
Advanced
Advanced
Mode 3
Normal
Normal
Description
Expanded mode with
on-chip ROM disabled
Single-chip mode
Expanded mode with
on-chip ROM enabled
Single-chip mode
Expanded mode with
on-chip ROM enabled
Mode Pins
MD1 MD0
0
1
1
0
1
MDCR
EXPE On-Chip ROM
1
Disabled
0
Enabled
1
(64 kbytes)
0
Enabled
1
(56 kbytes)
659