Renesas HD6417641 - Figure 13.22 Example of DREQ Input Detection in Cycle Steal Mode Level Detection When DACK Is Divided to 2 by Idle Cycles

Section 13 Direct Memory Access Controller (DMAC)
Rev. 4.00 Sep. 14, 2005 Page 449 of 982
REJ09B0023-0400
CPU
CPU
DMAC write
DMAC write
Non-sensitive period
1st acceptance 2nd acceptance
3rd acceptance possible
3rd acceptance possible
Non-sensitive period
Non-sensitive period
1st acceptance 2nd acceptance
Non-sensitive period
DREQ
(Overrun 1,
high-level)
DACK
(High-active)
CKIO
Bus cycle
DREQ
(Overrun 0,
high-level)
DACK
(High-active)
CKIO
Bus cycle
Figure 13.22 Example of DREQ Input Detection in Cycle Steal Mode Level Detection
When DACK is Divided to 2 by Idle Cycles
(3) Notes
For the external access described in (2) above, note the following.
1. When the DREQ edge is detected, input one DREQ edge at maximum in the bus cycle.
2. When the DREQ level is detected in overrun 0, negate the DREQ input in the bus cycle after
the detection of the first DACK output negation and before the second DACK output negation.
3. When the DREQ level is detected in overrun 1, negate DREQ input after the detection of the
first DACK output assertion and before the second DACK output assertion.