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7.2.2 Bus
Transfer
Timing
Even if a bus request is received from a bus master with a higher priority than that of the bus
master that has acquired the bus mastership and is currently operating, the bus mastership is not
necessarily transferred immediately. The CPU is the lowest-priority bus master, and if a bus
request is received from the DTC, the bus arbiter transfers the bus mastership to the bus master
that issued the request. The timing for transfer of the bus mastership is as follows:
•
The bus mastership is transferred at a break between bus cycles. However, if a bus cycle is
executed in discrete operations, as in the case of a longword-size access, the bus mastership is
not transferred between such operations. For details, refer to section 2.7, Bus Status in
Instruction Execution in the H8S/2600 Series, H8S/2000 Series Programming Manual.
•
If the CPU is in sleep mode, it transfers the bus mastership immediately.
The DTC can release the bus mastership after a vector read, a register information read (3 states),
a single data transfer, or a register information write (3 states). It does not release the bus
mastership during a register information read (3 states), a single data transfer, or a register
information write (3 states).
Summary of Contents for H8S/2627
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