M32CSLASH86 datasheet(148/505 Pages) RENESAS

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Page 125

13. DMAC

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13. DMAC

This microcomputer contains four DMAC (direct memory access controller) channels that allow data to be

sent to memory without using the CPU. DMAC transmits a 8- or 16-bit data from a source address to a

destination address whenever a transmit request occurs. DMA0 and DMA1 must be prioritized if using

DMAC. DMA2 and DMA3 share registers required for high-speed interrupts. High-speed interrupts cannot

be used when using three or more DMAC channels.

The CPU and DMAC use the same data bus, but DMAC has a higher bus access privilege than the CPU.

The cycle-steal method employed on DMAC enables high-speed operation between a transfer request and

the complete transmission of 16-bit (word) or 8-bit (byte) data. Figure 13.1 shows a mapping of registers to

be used for DMAC. Table 13.1 lists specifications of DMAC. Figures 13.2 to 13.5 show registers associ-

ated with DMAC.

Because the registers shown in Figure 13.1 are allocated in the CPU, use the LDC instruction to write to the

registers. To set the DCT2, DCT3, DRC2, DRC3, DMA2 and DMA3 registers, set the B flag to "1" (register

bank 1) and set the R0 to R3, A0, A1 registers with the MOV instruction.

To set the DSA2 and DSA3 registers, set the B flag to "1" and set the SB and FB registers with the LDC

instruction. To set the DRA2 and DRA3 registers, set the SVP and VCT registers with the LDC instruction.

DMA Mode Register 0

DMA 0 Transfer Count Register

DMA 0 Transfer Count Reload Register(1)

DMA 0 Memory Address Register

DMA 0 SFR Address Register

DMA 0 Memory Address Reload Register(1)

DMD0

DMD1

DCT0

DCT1

DRC0

DRC1

DMA0

DMA1

DSA0

DSA1

DRA0

DRA1

DMAC-Associated Registers

When Three or More DMAC Channels are Used,

the High-Speed Interrupt Register is Used as DMAC

Registers

DMA2 Transfer Count Register

DMA2 Transfer Count Reload Register(1)

DMA2 Memory Address Register

DMA2 SFR Address Register

DCT2 (R0)

DCT3 (R1)

DRC2 (R2)

DRC3 (R3)

DMA2 (A0)

DMA3 (A1)

DSA2 (SB)

DSA3 (FB)

When using DMA2 and DMA3, use the CPU registers shown in parentheses ().

When Three or More DMAC Channels are Used,

the Register Bank 1 is Used as DMAC Registers

DMA3 Transfer Count Register

DMA3 Transfer Count Reload Register(1)

DMA3 Memory Address Register

DMA3 SFR Address Register

SVF

DMA2 Memory Address Reload Register(1)

DRA2 (SVP)

DRA1 (VCT)

Flag Save Register

DMA3 Memory Address Reload Register(1)

DMA Mode Register 1

DMA 1 Transfer Count Register

DMA 1 Transfer Count Reload Register(1)

DMA 1 Memory Address Register

DMA 1 SFR Address Register

DMA 1 Memory Address Reload Register(1)

NOTES:

1. Registers are used for repeat transfer, not for single transfer.

Figure 13.1 Register Mapping for DMAC

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