h8s-2635 Renesas Electronics Corporation., h8s-2635 Datasheet - Page 858

• Manufacturer Part Number: h8s-2635
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

Section 21B ROM (H8S/2638 Group, H8S/2639 Group, H8S/2630 Group)
21B.1.2 Register Configuration
The H8S/2638 and H8S/2639 operating mode is controlled by the mode pins and the MDCR
register. The register configuration is shown in table 21B-1.
Table 21B-1 Register Configuration
Note: * Lower 16 bits of the address.
21B.2 Register Descriptions
21B.2.1 Mode Control Register (MDCR)
Note: * Determined by pins MD2 to MD0.
MDCR is an 8-bit register used to monitor the current H8S/2638 Group, H8S/2639 Group, and
H8S/2630 Group operating mode.
Bit 7—Reserved: Only 1 should be written to these bits.
Bits 6 to 3—Reserved: These bits are always read as 0 and cannot be modified.
Bits 2 to 0—Mode Select 2 to 0 (MDS2 to MDS0): These bits indicate the input levels at pins
MD2 to MD0 (the current operating mode). Bits MDS2 to MDS0 correspond to pins MD2 to
MD0. MDS2 to MDS0 are read-only bits, and cannot be modified. The mode pin (MD2 to MD0)
input levels are latched into these bits when MDCR is read. These latches are canceled by a reset.
21B.3 Operation
The on-chip ROM is connected to the CPU by a 16-bit data bus, and both byte and word data can
be 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.
Rev. 6.00 Feb 22, 2005 page 798 of 1484
REJ09B0103-0600
Register Name
Mode control register
Initial value:
R/W:
Bit:
R/W
—
7
1
Abbreviation
MDCR
—
—
6
0
—
—
5
0
R/W
R/W
—
—
4
0
—
—
Initial Value
Undefined
3
0
MDS2
— *
R
2
MDS1
Address*
H'FDE7
— *
R
1
MDS0
— *
R
0