r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 420

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 7 DMA Controller (DMAC)
(6)
At the start of activation source acceptance, a low level is detected in both DREQ pin falling edge
sensing and low level sensing. Similarly, in the case of an internal interrupt, the interrupt request
is detected. Therefore, a request is accepted from an internal interrupt or DREQ pin low level that
occurs before write to DMABCRL to enable transfer.
When the DMAC is activated, take any necessary steps to prevent an internal interrupt or DREQ
pin low level remaining from the end of the previous transfer, etc.
(7)
When the DTE bit in DMABCRL is cleared to 0 at the end of a transfer or by a forcible
termination, the selected internal interrupt request will be sent to the CPU or DTC even if the
DTA bit in DMABCRH is set to 1.
Also, if internal DMAC activation has already been initiated when operation is forcibly
terminated, the transfer is executed but flag clearing is not performed for the selected internal
interrupt even if the DTA bit is set to 1.
An internal interrupt request following the end of transfer or a forcible termination should be
handled by the CPU as necessary.
(8)
To reactivate a number of channels when multiple channels are enabled, use exclusive handling of
transfer end interrupts, and perform DMABCR control bit operations exclusively.
Note, in particular, that in cases where multiple interrupts are generated between reading and
writing of DMABCR, and a DMABCR operation is performed during new interrupt handling, the
DMABCR write data in the original interrupt handling routine will be incorrect, and the write may
invalidate the results of the operations by the multiple interrupts. Ensure that overlapping
DMABCR operations are not performed by multiple interrupts, and that there is no separation
between read and write operations by the use of a bit-manipulation instruction.
Also, when the DTE and DTME bits are cleared by the DMAC or are written with 0, they must
first be read while cleared to 0 before the CPU can write 1 to them.
Rev. 1.00 Sep. 19, 2008 Page 392 of 1270
REJ09B0466-0100
Activation Source Acceptance
Internal Interrupt after End of Transfer
Channel Re-Setting