3069RF-ZTAT Datasheet, PDF (265/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

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
[1]
DTE = 1
No
DTME = 0
Yes
Set DTME to 1
[2]
[1] Check that DTE = 1 and DTME = 0.
[2] Read DTCRB while DTME = 0,
then write 1 in the DTME bit.
DMA transfer continues
End
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.
Rev. 5.0, 09/04, page 243 of 978