SH7729R Datasheet, PDF (69/855 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer Super RISC engine Family/SH7700 Series

2.1.1 General Registers
There are sixteen 32-bit general registers (Rn), designated R0 to R15. The general registers are
used for data processing and address calculation.
With SuperH microcomputer type instructions, R0 is used as an index register. With a number of
instructions, R0 is the only register that can be used. R15 is used as the stack pointer (SP). In
exception handling, R15 is used to reference the stack when saving and restoring the status register
(SR) and program counter (PC).
With DSP type instructions, eight of the sixteen general registers are used for addressing of X and
Y data memory and data memory (single data) that uses the L-bus.
To access X memory, R4 and R5 are used as the X address register [Ax] and R8 is used as the X
index register [Ix]. To access Y memory, R6 and R7 are used as the Y address register [Ay] and
R9 is used as the Y index register [Iy]. To access single data that uses the L-bus, R2, R3, R4, and
R5 are used as the single data address register [As] and R8 is used as the single data index register
[Is].
Figure 2.3 shows the general registers, which are identical to those of the SH3, when DSP
extension is disabled.
31
0
R0^{*1 *2}
R1^*2
R2^*2
R3^*2
R4^*2
R5^*2
R6^*2
General Registers (when not in DSP mode)
Notes: 1. R0 functions as an index register in the
indexed register-indirect addressing mode
and indexed GBR-indirect addressing mode.
In some instructions, only R0 can be used as
the source register or destination register.
2. R0−R7 are banked registers. In user mode,
R7^*2
R8
R9
R10
BANK0 is used. In privileged mode, SR.RB
specifies BANK.
SR.RB = 0; BANK0 is used
SR.RB = 1; BANK1 is used
R11
R12
R13
R14
R15
Figure 2.3 General Purpose Registers (Not in DSP Mode)
Rev. 5.0, 09/03, page 23 of 806