h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 679

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

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
The on-chip flash memory 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
MCU
Operating
Mode
Mode 1
Mode 2
Mode 3
Operation
CPU
Operating
Mode
Normal
Advanced
Advanced
Normal
Normal
Section 22 ROM
Operating Mode
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
(H8S/2138 F-ZTAT A-Mask Version, H8S/2134 F-ZTAT A-Mask Version)
MD1
1
0
Rev. 4.00 Jun 06, 2006 page 625 of 1004
Mode Pins
MD0
1
0
1
MDCR
EXPE
1
0
1
0
1
REJ09B0301-0400
On-Chip ROM
Disabled
Enabled
(128 kbytes)
Enabled
(56 kbytes)