36
2.3.4
Mode 4 (Expanded Mode with On-Chip ROM Enabled)
The CPU can access a 16-Mbyte address space in advanced mode. The on-chip ROM is enabled.
Ports A, B, and C function as input ports immediately after a reset, but can be set to function as an
address bus. For details see section 5, I/O Ports. Port D functions as a data bus, and parts of ports
F and G carry bus control signals.
The initial bus mode after a reset is 8 bits, with 8-bit access to all areas. The program in on-chip
ROM connected to the first half of area 0 is executed. However, if 16-bit access is designated for
any area by the bus controller, the bus mode switches to 16 bits and port E functions as a data bus.
2.3.5
Mode 5 (External ROM Activation Expanded Mode with On-Chip ROM Enabled)
The CPU can access a 16-Mbyte address space in advanced mode. The on-chip ROM*
1
is enabled.
Ports A, B, and C function as an address bus, ports D and E function as a data bus, and parts of
ports F and G carry bus control signals.
The initial bus mode after a reset is 16 bits, with 16-bit access to all areas. The program in on-chip
ROM*
2
connected to the first half of area 0 is executed. However, if 8-bit access is designated for
any area by the bus controller, the bus mode switches to 8 bits.
Notes: 1. H8S/2678: H'100000 to H'180000; H8S/2675: H'100000 to H'140000
2. H8S/2678, H8S/2675: H'000000 to H'100000
2.3.6
Mode 6 (External ROM Activation Expanded Mode with On-Chip ROM Enabled)
This is an external ROM activation expanded mode with on-chip ROM disabled.
Operation is the same as in mode 5, except that the initial external bus mode after a reset is 8 bits.
2.3.7
Mode 7 (Single-Chip Activation Mode with On-Chip ROM Enabled)
The CPU can access a 16-Mbyte address space in advanced mode. The on-chip ROM is enabled,
and the chip starts up in single-chip mode. External addresses cannot be used in single-chip mode,
but they can be made accessible by means of a setting in the system control register (SYSCR).
When external addresses are enabled, settings can be made to designate ports A, B, and C for
address output, and ports D and E as data bus. For details see section 5, I/O Ports.
The initial mode after a reset is single-chip mode, with all I/O ports available for use as
input/output ports. However, the mode can be switched to externally expanded mode by means of
a setting in SYSCR. When externally expanded mode is selected, all areas are initially designated
as 16-bit access space. The function of pins in ports A to H is the same as in externally expanded
mode with on-chip ROM enabled.
Содержание H8S/2670
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