Chapter 8 DMA Controller
8-6
•
When edge detection is set (DMCCRn.EGREQ
=
1)
Please set up assertion of the DMAREQ[n] signal so the DMAREQ[n] signal is asserted
after the DMAACK[n] signal corresponding to a previously asserted DMAREQ[n] signal is
deasserted. The DMAREQ[n] signal will not be detected even if it is asserted before
DMAACK[n] is deasserted.
Figure 8.3.1 is a timing diagram that shows the timing of external DMA access. In this timing
diagram, both the DMAREQ[n] signal and the DMAACK[n] signal are set to Low active
(DMCCRn.REQPL = 0, DMCCRn.ACKPOL = 0).
The DMAACK[n] and DMADONE[n] signals, which are DMA control signals, are
synchronized to SDCLK. When these signals are used by an external I/O device that is
synchronous to SYSCLK, it is necessary to take clock skew into account.
The DMAACK[n] signal is asserted either at the SYSCLK cycle, the same as with assertion of
the CE*/CS* signal, or before that. In addition, it is deasserted after the last ACK*/READY signal
is deasserted.
When the DMADONE* signal (refer to 8.3.3.4) is used as an output signal, it is asserted for at
least one SYSCLK cycle while the DMAACK[n] signal is asserted either during the same
SYSCLK cycle that the CE*/CS* signal is deasserted or during a subsequent SYSCLK cycle.
When the DMADONE* signal is used as an input signal, it must be asserted for one SYSCLK
cycle while the DMAACK[n] signal is being asserted.
Figure 8.3.1 External I/O DMA Transfer (Single Address, Level Request)
1c040
SYSCLK
CE
*
ADDR [19:0]
ACE
*
OE
*
/BUSSPRT
*
SWE
*
BWE
*
DATA [31:0]
ACK
*
DMAREQ[n]
DMAACK[n]
DMADONE
*
00040
f
00000100
1 cycle
Summary of Contents for TX49 TMPR4937
Page 1: ...64 Bit TX System RISC TX49 Family TMPR4937 Rev 2 0 ...
Page 4: ......
Page 13: ...Table of Contents ix TMPR4937 Revision History 1 ...
Page 14: ...Table of Contents x ...
Page 15: ...Handling Precautions ...
Page 16: ......
Page 18: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 40: ...3 General Safety Precautions and Usage Considerations 3 18 ...
Page 42: ...4 Precautions and Usage Considerations 4 2 ...
Page 43: ...TMPR4937 2005 3 Rev 2 0 ...
Page 44: ......
Page 52: ...Chapter 1 Overview and Features 1 6 ...
Page 156: ...Chapter 7 External Bus Controller 7 56 ...
Page 491: ...Chapter 16 Removed 16 1 16 Removed ...
Page 492: ...Chapter 16 Removed 16 2 ...
Page 493: ...Chapter 17 Removed 17 1 17 Removed ...
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Page 497: ...Chapter 19 Removed 19 1 19 Removed ...
Page 498: ...Chapter 19 Removed 19 2 ...
Page 506: ...Chapter 20 Extended EJTAG Interface 20 8 ...
Page 530: ...Chapter 22 Pinout and Package Information 22 10 ...
Page 542: ...Chapter 24 Parts Number when Ordering 24 2 ...