HD6417751RBP240V Datasheet, PDF (621/1226 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

14. Direct Memory Access Controller (DMAC)
Table 14.4 Selecting External Request Mode with RS Bits
RS3 RS2 RS1 RS0 Address Mode Transfer Source Transfer Destination
0
0
0
0
Dual address External memory, External memory,
mode
memory-mapped memory-mapped
external device, or external device, or
external device with external device with
DACK
DACK
1
0
Single address External memory External device
mode
or memory-mapped with DACK
external device
1
Single address External device with External memory
mode
DACK
or memory-mapped
external device
• External Request Acceptance Conditions
1. When at least one of DMAOR.DME and CHCR.DE is 0, and DMAOR.NMIF,
DMAOR.AE, and CHCR.TE are all 0, if an external request (DREQ: edge-detected) is
input it will be held inside the DMAC until DMA transfer is either executed or canceled.
Since DMA transfer is not enabled in this case (DME = 0 or DE = 0), DMA transfer is not
initiated. DMA transfer is started after it is enabled (DME = 1, DE = 1, DMAOR.NMIF =
0, DMAOR.AE = 0, CHCR.TE = 0).
2. When DMA transfer is enabled (DME = 1, DE = 1, DMAOR.NMIF = 0, DMAOR.AE = 0,
CHCR.TE = 0), if an external request (DREQ) is input, DMA transfer is started.
3. An external request (DREQ) will be ignored if input when CHCR.TE = 1, DMAOR.NMIF
= 1, DMAOR.AE = 1, during a power-on reset or manual reset, in deep sleep mode,
standby mode, or while the DMAC is in the module standby state.
4. A previously input external request will be canceled by the occurrence of an NMI interrupt
(DMAOR.NMIF = 1) or address error (DMAOR.AE = 1), or by a power-on reset or
manual reset.
• Usage Notes
1. An external request (DREQ) is detected by a low level or falling edge. Ensure that the
external request (DREQ) signal is held high when there is no DMA transfer request from
an external device after a power-on reset or manual reset.
When DMA transfer is restarted, check whether a DMA transfer request is being held.
2. With DREQ edge detection, an accepted external request can be canceled by first negating
DREQ, enabling a change of setting from CHCR.DS = 1 to CHCR.DS = 0, and then
asserting DREQ after setting CHCR.DS to 1 again.
Rev.4.00 Oct. 10, 2008 Page 521 of 1122
REJ09B0370-0400