H8S-2350 RENESAS [Renesas Technology Corp], H8S-2350 Datasheet - Page 226

• Manufacturer Part Number: H8S-2350
• Description: 16-Bit Single-Chip Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 6 Bus Controller
6.11.3
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 and is currently operating, the bus is not necessarily transferred
immediately. There are specific times at which each bus master can relinquish the bus.
CPU
The CPU is the lowest-priority bus master, and if a bus request is received from the DTC or
DMAC, the bus arbiter transfers the bus to the bus master that issued the request. The timing for
transfer of the bus is as follows:
DTC
The DTC sends the bus arbiter a request for the bus when an activation request is generated.
The DTC can release the bus 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 during a register
information read (3 states), a single data transfer, or a register information write (3 states).
DMAC
The DMAC sends the bus arbiter a request for the bus when an activation request is generated.
In the case of an external request in short address mode or normal mode, and in cycle steal mode,
the DMAC releases the bus after a single transfer.
In block transfer mode, it releases the bus after transfer of one block, and in burst mode, after
completion of a transfer.
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REJ09B0330-0300
The bus 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 is not transferred between
the operations. See appendix A.5, Bus States during Instruction Execution, for timings at
which the bus is not transferred.
If the CPU is in sleep mode, it transfers the bus immediately.
Bus Transfer Timing