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7721 Group User’s Manual

13-25

DMA CONTROLLER

13.3 Control

13.3.5 Termination of DMA transfer

As the methods of terminating DMA transfer, normal and forced termination are used.

(1)

Normal termination

All of the DMAi transfers terminate and DMAC stops. This method is used in the single transfer, array

chain transfer, and link array chain transfer modes. In the repeat transfer mode, however, normal

termination cannot be applied to terminating transfer; then, forced termination must be used. (Refer

to “(2) Forced termination” of this section.)

Table 13.3.4 lists the states of DMAC at normal termination.

Table 13.3.4 States of DMAC at normal termination

Item

State

DMAi interrupt request bit

DMAi request bit

DMAi enable bit

___

output

Channel priority levels

In the burst transfer mode (edge sense): 0

In the burst transfer mode (level sense): not changed

In the cycle-steal transfer mode: not changed (Note)

___

Outputs “L” (when the TC pin is valid)

Rotating (when the rotating priority is selected)

Note: In the cycle-steal transfer mode, the DMAi request bit is cleared to “0” when a DMA request is

accepted. This bit is does not change at normal termination.

At normal termination, the CPU regains the right to use bus after the terminate processing (3 cycles

φ) via the transition of the right to use bus (1 cycle of φ). Figure 13.3.3 shows a timing example

at normal termination.

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