H8SLASH3028F datasheet(267/923 Pages) RENESAS

No. de pieza	H8/3028F

Descripción Electrónicos	Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

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Fabricante Electrónico	RENESAS [Renesas Technology Corp]

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267 / 923 page

Rev. 2.00, 09/03, page 237 of 890

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

Check that DTE = 1 and DTME = 0.

Read DTCRB while DTME = 0,

then write 1 in the DTME bit.

Yes

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.

H8/3028F Datasheet(PDF) 267 Page - Renesas Technology Corp