H83069RF datasheet(265/1003 Pages) RENESAS

265 / 1003 page

Rev. 5.0, 09/04, page 243 of 978

7.4.11

NMI Interrupts and DMAC

NMI interrupts do not affect DMAC operations in short address mode.

If an NMI interrupt occurs during a transfer in full address mode, the DMAC suspends operations.

In full address mode, a channel is enabled when its DTE and DTME bits are both set to 1. NMI

input clears the DTME bit to 0. After transferring the current byte or word, the DMAC releases

the bus to the CPU. In normal mode, the suspended transfer resumes when the CPU sets the

DTME bit to 1 again. Check that the DTE bit is set to 1 and the DTME bit is cleared to 0 before

setting the DTME bit to 1.

Figure 7.21 shows the procedure for resuming a DMAC transfer in normal mode on channel 0

after the transfer was halted by NMI input.

Resuming DMAC transfer

in normal mode

DTE = 1

DTME = 0

Set DTME to 1

DMA transfer continues

End

[1]

[2]

Check that DTE = 1 and DTME = 0.

Read DTCRB while DTME = 0,

then write 1 in the DTME bit.

[2]

Yes

[1]

Figure 7.21 Procedure for Resuming a DMAC Transfer Halted by NMI (Example)

For information about NMI interrupts in block transfer mode, see section 7.6.6, NMI Interrupts

and Block Transfer Mode.

H83069RF Datasheet(PDF) 265 Page - Renesas Technology Corp