CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
User’s Manual U12688EJ4V0UM00
175
6.4
DMA Bus States
6.4.1 Types of bus states
The DMAC bus cycle consists of the following 25 states:
(1)
TI state
The TI state is idle state, during which no access request is issued.
The DMARQ0 to DMARQ3 signals are sampled at the falling edge of the CLKOUT signal.
(2)
T0 state
DMA transfer ready state. (A DMA transfer request has been issued, causing bus mastership to be acquired
for the first DMA transfer).
(3)
T1R state
The bus enters the T1R state at the beginning of a read operation in two-cycle transfer mode. Address
driving starts. After entering the T1R state, the bus invariably enters the T2R state.
(4)
T1RI state
T1RI is a state in which the bus is waiting for the acknowledge in response to an external memory read
request. After entering the last T1RI state, the bus invariably enters the T2R state.
(5)
T2R state
The T2R state corresponds to the last state of a read operation in 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
Internal peripheral I/O or internal RAM DMA transfer ready state (Bus mastership is acquired for DMA transfer
to internal 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 two-cycle transfer mode. Address
driving starts. After entering the T1W state, the bus invariably enters the T2W state.
(8)
T1WI state
T1WI is a state in which the bus is waiting for the acknowledge signal in response to an external memory
write request. After entering the last T1WI state, the bus invariably enters the T2W state.
(9)
T2W state
The T2W state corresponds to the last state of a write operation in two-cycle transfer mode, or to a wait state.
In the last T2W state, the write strobe signal is made inactive.
(10) T1F state
The bus enters the T1F state at the beginning of a flyby transfer from internal peripheral I/O to internal RAM.
The read cycle from internal peripheral I/O is started. After entering the T1F state, the bus invariably enters
the T2F state.
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