SH7144_08 Datasheet, PDF (243/930 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family/SH7144 Series

10. Direct Memory Access Controller (DMAC)
and the DACK signal is not output. Nor is the number of DMAC transfers counted. The actual
DMAC transfer begins after one dummy bus cycle output.
The dummy cycle is not counted either at the start of the second sampling (transfer one bus cycle
before the start of the first DMAC transfer). Therefore, the second sampling is not conducted from
the bus cycle starting the dummy cycle, but from the start of the CPU(3) bus cycle.
Thereafter, as long the DREQ is continuously sampled, no dummy cycle is inserted. DREQ
sampling timing during this period begins from the start of the transfer one bus cycle before the
start of DMAC transfer, in the same way as with cycle steal mode.
As with the fourth sampling in figure 10.20, once DMAC transfer is interrupted, a dummy cycle is
again inserted at the start as soon as DMAC transfer is resumed.
The DACK output period in burst mode is the same as in cycle steal mode.
Burst Mode, Dual Address, and Edge Detection: In burst mode with dual address and edge
detection, DREQ sampling is conducted only on the first cycle.
In figure 10.22, DMAC transfer begins, at the earliest, three cycles after the timing of the first
sampling. Thereafter, DMAC transfer continues until the end of the data transfer count set in the
DMATCR. DREQ sampling is not conducted during this period. Therefore, DRAK is output on
the first cycle only.
When DMAC transfer is resumed after being halted by an NMI or address error, be sure to reinput
an edge request. The remaining transfer restarts after the first DRAK output.
The DACK output period in burst mode is the same as in cycle steal mode.
Burst Mode, Single Address, and Edge Detection: In burst mode with single address and edge
detection, DREQ sampling is conducted only on the first cycle. In figure 10.23, a dummy cycle is
inserted, at the earliest, three cycles after the timing for the first sampling. During this period, data
is undefined, and DACK is not output. Nor is the number of DMAC transfers counted. Thereafter,
DMAC transfer continues until the data transfer count set in the DMATCR has ended. DREQ
sampling is not conducted during this period. Therefore, DRAK is output on the first cycle only.
When DMAC transfer is resumed after being halted by an NMI or address error, be sure to reinput
an edge request. DRAK is output once, and the remaining transfer restarts after output of one
dummy cycle.
The DACK output period in burst mode is the same as in cycle steal mode.
Rev.4.00 Mar. 27, 2008 Page 199 of 882
REJ09B0108-0400