184
Chapter 7
DMA Functions (DMA Controller)
Preliminary User’s Manual U15839EE1V0UM00
7.4 DMA
Bus
States
7.4.1 Types of bus states
The DMAC bus states consist of the following 13 states.
(1)
TI state
The TI state is an idle state, during which no access request is issued.
(2)
T0 state
This is the DMA transfer ready state (state in which a DMA transfer request has been issued and
the bus mastership is acquired for the first DMA transfer).
(3)
T1R state
The bus enters the T1R state at the beginning of a read operation in the two-cycle transfer mode.
Address driving starts. After entering the T1R state, the bus invariably enters the T2R state.
(4)
T1RI state
This is a state in which the DMAC is awaiting an acknowledge signal for an external memory read
request. After the last T1RI state, the DMAC always transitions to the T2R state.
(5)
T2R state
The T2R state corresponds to the last state of a read operation in the two-cycle transfer mode, or
to a wait state.
In the last T2R state, read data is sampled. After entering the last T2R state, the bus invariably
enters the T1W state.
(6)
T2RI state
State in which the bus is ready for DMA transfer to on-chip peripheral I/O or internal RAM (state in
which the bus mastership is acquired for DMA transfer to on-chip peripheral I/O or internal RAM).
After entering the last T2RI state, the bus invariably enters the T1W state.
(7)
T1W state
The bus enters the T1W state at the beginning of a write operation in the two-cycle transfer mode.
Address driving starts. After entering the T1W state, the bus invariably enters the T2W state.
(8)
T1WI state
This is a state in which the DMAC is awaiting an acknowledge signal for an external memory write
request. After the last T1WI state, the DMAC always transitions to the T2W state.
(9)
T2W state
The T2W state corresponds to the last state of a write operation in the two-cycle transfer mode, or
to a wait state.
In the last T2W state, the write strobe signal is made inactive.
(10) T1FH state
This is the basic state of a flyby
Note
transfer and is the execution cycle of that transfer. After the
T1FH state, the DMAC transitions to the T2FH state.
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