SH7727 Datasheet, PDF (98/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

Section 2 CPU
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 [ ].
31
0
R0
General Registers (DSP mode enabled)
R1
R2 [As]
R3 [As]
R4 [As, Ax]
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.
R5 [As, Ax]
R6 [Ay]
R7 [Ay]
R8 [Ix, Is]
R9 [Iy]
R10
R11
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.
R12
R13
R14
R15
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)
Rev. 5.00 Dec 12, 2005 page 26 of 1034
REJ09B0254-0500