HD64F2149YV datasheet(717/1075 Pages) RENESAS

717 / 1075 page

Section 22 ROM

Rev. 3.00 Jan 18, 2006 page 689 of 1044

REJ09B0280-0300

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

Mode Pins

MDCR

MCU

Operating

Mode

CPU

Operating

Mode

Description

MD1

MD0

EXPE

On-Chip ROM

Mode 1

Normal

Expanded mode with

on-chip ROM disabled

1Disabled

Mode 2

Advanced

Single-chip mode

Advanced

Expanded mode with

on-chip ROM enabled

Enabled

(64 kbytes)

Mode 3

Normal

Single-chip mode

Normal

Expanded mode with

on-chip ROM enabled

Enabled

(56 kbytes)

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