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7.1
Overview
The H8S/2646 Series has a built-in bus controller (BSC) that manages the external address space
divided into eight areas. The bus specifications, such as bus width and number of access states,
can be set independently for each area, enabling multiple memories to be connected easily.
The bus controller also has a bus arbitration function, and controls the operation of the internal bus
masters: the CPU, and data transfer controller (DTC).
7.1.1
Features
The features of the bus controller are listed below.
• Manages external address space in area units
Manages the external space as 8 areas of 2-Mbytes
Bus specifications can be set independently for each area
Burst ROM interface can be set
• Basic bus interface
8-bit access or 16-bit access can be selected for each area
2-state access or 3-state access can be selected for each area
Program wait states can be inserted for each area
• Burst ROM interface
Burst ROM interface can be set for area 0
Choice of 1- or 2-state burst access
• Idle cycle insertion
An idle cycle can be inserted in case of an external read cycle between different areas
An idle cycle can be inserted in case of an external write cycle immediately after an
external read cycle
• Write buffer functions
External write cycle and internal access can be executed in parallel
• Bus arbitration function
Includes a bus arbiter that arbitrates bus mastership among the CPU and DTC
• Other
External bus release function
Section 7 Bus Controller
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