p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 100

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 3 MCU Operating Modes
3.3
3.3.1
The CPU can access a 16-Mbyte address space in advanced mode. The on-chip ROM is disabled.
Ports 1 and 2 function as an address bus, port 3 functions as a data bus, and part of port 4 carries
bus control signals. However, as these series have a maximum of 16 address outputs, an external
address can be specified correctly only when the I/O strobe function of the AS/IOS pin is used.
Mode 1 does not support on-chip emulation.
3.3.2
The CPU can access a 16-Mbyte address space in advanced mode. The on-chip ROM is enabled.
After a reset, single-chip mode is set, and the EXPE bit in MDCR must be set to 1 in order to use
external addresses. However, as these series have a maximum of 16 address outputs, an external
address can be specified correctly only when the I/O strobe function of the AS/IOS pin is used.
When the EXPE bit in MDCR is set to 1, ports 1 and 2 function as input ports after a reset. They
can be set to output addresses by setting the corresponding bits in the data direction register
(DDR) to 1. Port 3 functions as a data bus, and part of port 4 carries bus control signals.
3.3.3
The CPU can access a 64-Kbyte address space in normal mode. The on-chip ROM is enabled.
After a reset, single-chip mode is set, and the EXPE bit in MDCR must be set to 1 in order to use
external addresses.
When the EXPE bit in MDCR is set to 1, ports 1 and 2 function as input ports after a reset. They
can be set to output addresses by setting the corresponding bits in the data direction register
(DDR) to 1. Port 3 functions as a data bus, and part of port 4 carries bus control signals.
In this operating mode, the amount of on-chip ROM is limited to 56 Kbytes and the amount of on-
chip RAM is limited to 4 Kbytes.
Rev. 1.00 Sep. 21, 2006 Page 62 of 658
REJ09B0310-0100
Operating Mode Descriptions
Mode 1
Mode 2
Mode 3