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
mode
External memory
External memory
or memory-mapped or memory-mapped
external device, or external device, or
external device with external device with
DACK
DACK
1
0
1
Single address
mode
External memory
or memory-mapped with DACK
external device
External device
Single address
mode
External device with External memory
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 ('5(4: 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 ('5(4) is input, DMA transfer is started.
3. An external request ('5(4) will be ignored if input when CHCR.TE = 1, DMAOR.NMIF
= 1, or DMAOR.AE = 1, or during a power-on reset or manual reset, in deep sleep mode or
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.
In the SH7750S, it is possible to cancel a previously input external request ('5(4). With
DMAOR.COD set to 1, clear CHCRn.DS to 0 and then drive the '5(4 pin high.
On the SH7750R, it is possible to cancel an external request that has been accepted by
external request ('5(4) edge detection by first negating '5(4 and then clearing
CHCR.DS from 1 to 0. Afterwards CHCR.DS should be reset to 1 and '5(4 asserted.
(The SH7750R has no DMAOR.COD bit, but it is possible to cancel an external request
that has been accepted by external request ('5(4) edge detection, as is the case when the
DMAOR.COD bit of the SH7750S is set to 1.)
•
Usage Notes
An external request ('5(4) is detected by a low level or falling edge. Ensure that the external
request ('5(4) signal is held high when there is no DMA transfer request from an external
device after a power-on reset or manual reset.
Rev. 6.0, 07/02, page 513 of 986
RENESAS [ RENESAS TECHNOLOGY CORP ]
