CHAPTER 4 BUS CONTROL FUNCTION
User’s Manual U13850EJ6V0UD
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4.9 Bus Priority
There are four external bus cycles: bus hold, memory access, instruction fetch (branch), and instruction fetch
(continuous). The bus hold cycle is given the highest priority, followed by memory access, instruction fetch (branch),
and instruction fetch (continuous) in that order.
The instruction fetch cycle may be inserted between the read access and write access in a read-modify-write
access.
No instruction fetch cycle is inserted between the lower halfword access and higher halfword access of word
access operations.
Table 4-3. Bus Priority
External Bus Cycle
Priority
Bus hold
1
Memory access
2
Instruction fetch (branch)
3
Instruction fetch (continuous)
4
Содержание V850/SB1
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