SH7727 datasheet(98/1109 Pages) RENESAS

98 / 1109 page

Section 2 CPU

Rev. 5.00 Dec 12, 2005 page 26 of 1034

REJ09B0254-0500

On the other hand, R2 to R9 registers are also used for the DSP data address calculations, see

figure 2.4, when DSP extension is enabled. Another symbol that represents the purpose of the

registers in DSP type instruction is [ ].

R2 [As]

R3 [As]

R4 [As, Ax]

R5 [As, Ax]

R6 [Ay]

R7 [Ay]

R8 [Ix, Is]

R9 [Iy]

R10

R11

R12

R13

R14

R15

General Registers (DSP mode enabled)

X or Y data transfer operation

R4, R5 [Ax]:

Address register set for X data memory.

R8 [x]:

Index register for address register set Ax.

R6, R7 [Ay]:

Address register set for Y data memory.

R9 [Iy]:

Index register for address register set Ay.

Single data transfer operation

R2 to R5 [As]: Address register set for memory.

R8 [Is]:

Index register for address register set As.

Figure 2.4 General Purpose Register (DSP Mode)

DSP type instructions can access X and Y data memory simultaneously. To specify addresses for

X and Y data memory, two address pointer sets are prepared. These are:

R8[Ix], R4, R5[Ax] for X memory access, and R9[Iy], R6, R7[Ay] for Y memory access.

The names (symbol) R2 to R9 are used in the Assembler, but users can use other register names

that represent the purpose of the register in the DSP instruction explicitly. In the assembly

program, user can use an alias for the register. The coding in assembler is as follows.

Ix: .REG (R8)

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