SH7751 Datasheet, PDF (595/1224 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

14. Direct Memory Access Controller (DMAC)
Section 14 Direct Memory Access Controller (DMAC)
14.1 Overview
The SH7751 includes an on-chip four-channel direct memory access controller (DMAC). The
SH7751R has an on-chip eight-channel DMAC. The DMAC can be used in place of the CPU to
perform high-speed data transfers among external devices equipped with DACK (DMA transfer
end notification), external memories, memory-mapped external devices, and on-chip peripheral
modules (TMU, RTC, SCI, SCIF, CPG, and INTC). Using the DMAC reduces the burden on the
CPU and increases the operating efficiency of the chip. When using the SH7751R, see section
14.6, Configuration of the DMAC (SH7751R), section 14.7, Register Descriptions (SH7751R),
and section 14.8, Operation (SH7751R).
14.1.1 Features
The DMAC has the following features.
• Four channels (SH7751), eight channels (SH7751R)
• Physical address space
• Choice of 8-bit, 16-bit, 32-bit, 64-bit, or 32-byte transfer data length
• Maximum of 16 M (16,777,216) transfers
• Choice of single or dual address mode
⎯ Single address mode: Either the transfer source or the transfer destination (external device)
is accessed by a DACK signal while the other is accessed by address. One data transfer is
completed in one bus cycle.
⎯ Dual address mode: Both the transfer source and transfer destination are accessed by
address. Values set in DMAC internal registers indicate the accessed address for both the
transfer source and the transfer destination. Two bus cycles are required for one data
transfer.
• Choice of bus mode: cycle steal mode or burst mode
• Two types of DMAC channel priority ranking:
⎯ Fixed priority mode: Channel priorities are permanently fixed.
⎯ Round robin mode: Sets the lowest priority for the channel that last received an execution
request.
• An interrupt request can be sent to the CPU on completion of the specified number of
transfers.
Rev.4.00 Oct. 10, 2008 Page 497 of 1122
REJ09B0370-0400