379
Individual Channel Ending Conditions: There are two ending conditions. A transfer ends when
the value of the channel’s DMA transfer count register (DMATCR) is 0, or when the DE bit in the
channel’s CHCR register is cleared to 0.
•
When DMATCR is 0: When the DMATCR value becomes 0 and the corresponding channel's
DMA transfer ends, the transfer end flag bit (TE) is set in CHCR. If the IE (interrupt enable)
bit has been set, a DMAC interrupt (DEI) request is sent to the CPU. This transfer ending does
not apply to (a) through (d) described above.
•
When DE in CHCR is 0: Software can halt a DMA transfer by clearing the DE bit in the
channel’s CHCR register. The TE bit is not set when this happens. This transfer ending applies
to (a) through (d) described above.
Conditions for Ending on All Channels Simultaneously: Transfers on all channels end when 1)
the AE or NMIF (NMI flag) bit is set to 1 in DMAOR, or 2) when the DME bit in DMAOR is
cleared to 0.
•
Transfer ending when the NMIF bit is set to 1 in DMAOR: When an NMI interrupt occurs, the
AE or NMIF bit is set to 1 in DMAOR and all channels stop their transfers according to the
conditions in (a) to (d) described above, and pass the bus to an other bus master. Consequently,
even if the AE or NMI bit is set to 1 during transfer, SAR, DAR, DMATCR are updated. The
TE bit is not set. To resume transfer after NMI interrupt exception handling, clear the NMIF
bit to 0. At this time, if there are channels that should not be restarted, clear the corresponding
DE bit in CHCR.
•
Transfer ending when DME is cleared to 0 in DMAOR: Clearing the DME bit to 0 in DMAOR
forcibly aborts transfer on all channels. The TE bit is not set. All channels abort their transfer
according to the conditions in (a) to (d) in 11.3.7, DMA Transfer Ending Conditions, as in
NMI interrupt generation. In this case, the values in SAR, DAR, and DMATCR are also
updated.
Содержание SH7709S
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Страница 292: ...273 T1 CKIO A25 to A0 CSn RD WR RD D31 to D0 WEn D31 to D0 BS T2 Read Write Figure 10 6 Basic Timing of Basic Interface ...
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