Hitachi SH7751 Hardware Manual page 556

Conditions for Ending Transfer on Individual Channels: Transfer ends on the corresponding
channel when either of the following conditions is satisfied:


The value in the DMA transfer count register (DMATCR) reaches 0.


The DE bit in the DMA channel control register (CHCR) is cleared to 0.
1. End of transfer when DMATCR = 0
When the DMATCR value reaches 0, DMA transfer ends on the corresponding channel and
the transfer end flag (TE) in CHCR is set. If the interrupt enable bit (IE) is set at this time, an
interrupt (DMTE) request is sent to the CPU.
Transfer ending when DMATCR = 0 does not follow the procedures described in 1, 2, 3, and 4
in section 14.3.6.
2. End of transfer when DE = 0 in CHCR
When the DMA enable bit (DE) in CHCR is cleared, DMA transfer is suspended on the
corresponding channel. The TE bit is not set in this case. Transfer ending in this case follows
the procedures described in 1, 2, 3, and 4 in section 14.3.6.
Conditions for Ending Transfer Simultaneously on All Channels: Transfer ends on all
channels simultaneously when either of the following conditions is satisfied:


The address error bit (AE) or NMI flag (NMIF) in the DMA operation register (DMAOR) is
set.


The DMA master enable bit (DME) in DMAOR is cleared to 0.
1. End of transfer when AE = 1 in DMAOR
If the AE bit in DMAOR is set to 1 due to an address error, DMA transfer is suspended on all
channels in accordance with the conditions in 1, 2, 3, and 4 in section 14.3.6, and the bus is
passed to the CPU. Therefore, when AE is set to 1, the values in the DMA source address
register (SAR), DMA destination address register (DAR), and DMA transfer count register
(DMATCR) indicate the addresses for the DMA transfer to be performed next and the
remaining number of transfers. The TE bit is not set in this case. Before resuming transfer, it is
necessary to make a new setting for the channel that caused the address error, then write 0 to
the AE bit after first reading 1 from it. Acceptance of external requests is suspended while AE
is set to 1, so a DMA transfer request must be reissued when resuming transfer. Acceptance of
internal requests is also suspended, so when resuming transfer, the DMA transfer request
enable bit for the relevant on-chip peripheral module must be cleared to 0 before the new
setting is made.
Rev. 3.0, 04/02, page 517 of 1064