Datasheet

Section 7 DMA Controller (DMAC)
R01UH0310EJ0500 Rev. 5.00 Page 405 of 1384
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
(5) Activation by Falling Edge on DREQ Pin
DREQ pin falling edge detection is performed in synchronization with DMAC internal operations.
The operation is as follows:
[1] Activation request wait state: Waits for detection of a low level on the DREQ pin, and
switches to [2].
[2] Transfer wait state: Waits for DMAC data transfer to become possible, and switches to [3].
[3] Activation request disabled state: Waits for detection of a high level on the DREQ pin, and
switches to [1].
After DMAC transfer is enabled, a transition is made to [1]. Thus, initial activation after transfer is
enabled is performed on detection of a low level.
(6) Activation Source Acceptance
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) Internal Interrupt after End of Transfer
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.