Section 14 Direct Memory Access Controller (DMAC)
Rev.1.00 Dec. 13, 2005 Page 609 of 1286
REJ09B0158-0100
14.5.4 DACK
output division
The DACK output is divided to align the data unit like the
CSn
output when a DMA transfer unit
is divided with multiple bus cycles, for example when an 8-bit or 16-bit external device is
accessed in longword units, or when an 8-bit external device is accessed in word units, and the
CSn
output is negated between these bus cycles.
14.5.5 Clear
DMINT
Interrupt
To ensure that a DMINT interrupt source that should have been cleared is not inadvertently
accepted again, clear the BL bit after confirming the corresponding flag in INT2B3 register
becomes 0 or issue the RTE instruction.
14.5.6
CS
Output Settings and Transfer Size Larger than External Bus Width
When one DMA transfer is performed by multiple bus cycles*
1
, the
CSn
output should be set not
to negate between bus cycles*
2
. For detail of settings, refer to table 11.11 to 11.14. If set the
CSn
output is negated between bus cycles, the DREQ signal is not sampled correctly and malfunction
may occur.
Notes: 1. When a DMA transfer is performed with larger transfer size than the bus width. For
example, performing the 16-/32-byte transfer to the 8-/16-/32-bit bus width LBSC
space, longword (32-bit) transfer to the 8-/16-bit bus width LBSC space, or word (16-
bit) transfer to the 8-bit bus width LBSC space. Note that except for a 32-bit access to
the MPX interface. This access generates only one bus cycle (burst).
2.
When
the
CSn
output is negated between bus cycles, then the DACK output is also
negated between bus cycles (DACK output is also divided).
14.5.7
DACK Assertion and DREQ Sampling
The DACK signal may be asserted ceaselessly during two or more times DMA transfer when the
DREQ level detection with overrun 1 and the DREQ edge detection. In this case, the DMA
transfer is suspended and do not perform correctly, to avoid this insert one or more idle cycle
between the DMA transfer.
The transfer source is the LBSC space and the DACK is output during the read cycle:
(1) Set B'001 to B'111 (i.e., other than 000) to the IWRRD bits in CSnBCR
(2) Set B'001 to B'111 (i.e., other than 000) to the IWRRS bits in CSnBCR
Содержание SH7780 Series
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Страница 450: ...Section 11 Local Bus State Controller LBSC Rev 1 00 Dec 13 2005 Page 400 of 1286 REJ09B0158 0100 ...
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