Renesas SH7781 - Manual (Page 751)

14. Direct Memory Access Controller (DMAC)
Rev.1.00 Jan. 10, 2008 Page 721 of 1658
REJ09B0261-0100
14.4.7 DREQ Pin Sampling Timing
Figures 14.13 to 14.22 show the timing that the DREQ input is sampled in each bus mode.
Figures 14.13, 14.16, and 14.20 show the timing that the DREQ input is sampled when byte
transfer is performed in 8-, 16-, 32-, or 64-bit bus width, word transfer is performed in 16-, 32-, or
64-bit bus width, or longword transfer is performed in 32- or 64-bit bus width. DACK is output
once in DMA1 transfer.
Figures 14.14, 14.17, and 14.21 show the timing that the DREQ input is sampled when word
transfer is performed in 8-bit bus width, longword transfer is performed in 8- or 16-bit bus width,
or 16- or 32-byte transfer is performed in 8-, 16-, 32-, or 64-bit bus width. These figures suppose
that DACK of DMA1 transfer is divided.
Figures 14.15, 14.18, and 14.22 show the timing that the DREQ input is sampled when word
transfer is performed in 8-bit bus width, longword transfer is performed in 8- or 16-bit bus width,
or 16- or 32-byte transfer is performed in 8-, 16-, 32-, or 64-bit bus width. These figures suppose
that DACK of DMA1 transfer is connected.
When word transfer is performed in 8-bit bus width, longword transfer is performed in 8- or 16-bit
bus width, or 16- or 32-byte transfer is performed in 8-, 16-, 32-, or 64-bit bus width, DMA
transfer units are divided into multiple bus cycles. If DMA transfer size is divided into multiple
bus cycles and CS is negated between bus cycles, DACK output is divided, like CS. For details,
see section 11.5.16, Register Settings for Divided-Up
DACKn Output.
CLKOUT
Bus cycle
DREQ
(Rising edge)
DRAK
(High-active)
DACK
(High-active)
: Non-sensitive period Accepted after one cycle of CLKOUT
at the rising edge of DACK
CPU DMAC CPU
1st acceptance 2nd acceptance
Acceptance started
Figure 14.13 Example 1 of DREQ Input Detection in Cycle Steal Mode Edge Detection
(Byte Transfer in 8/16/32/64-Bit Bus Width, Word Transfer in 16/32/64-Bit Bus Width, or
Longword Transfer in 32/64-Bit Bus Width)