SH3-DSP Control Registers
The SH3-DSP has eight control registers. The DSP mode is started only when SR.DSP = 1.
| Control Register | Description |
|---|---|
| SSR | Same as the corresponding SH-3 registers. |
| SPC | Same as the corresponding SH-3 registers. |
| GBR | Same as the corresponding SH-3 registers. |
| VBR | Same as the corresponding SH-3 registers. |
| RS | Repeat start register. |
| RE | Repeat end register. |
| RC | Repeat counter register. |
| RF0, RF1 | Repeat control bit. |
| MOD | Modulo register. |
| DMX,DMY | Modulo control bits in SR. |
Note You cannot operate both X and Y address pointers in modulo addressing mode even if you set both DMX and DMY bits. The case where DMX = DMY = 1 is reserved for future expansion. If both DMX and DMY are set simultaneously, the hardware treats the Y address pointer as the modulo-addressing pointer. Modulo addressing is available for X and Y data transfer operations MOVX and MOVY, but not for the single data transfer operation MOVS.
In order to access Repeat Start (RS), Repeat End (RE), and Modulo (ME) Control Registers, SH3-DSP provides load and store instructions for these registers.
The following example shows how to use RS.
LDC Rm,RS; Rm -> RS
LDC.L @Rm+,RS; (Rm) -> RS, Rm+4 -> Rm
STC RS,Rn; RS -> Rn
STC.L RS,@-Rn; Rn-4 -> Rn, RS -> (Rn)
The following address-set instructions apply to RS and RE.
LDRS @(disp,PC); disp 2 + PC -> RS
LDRE @(disp,PC); disp 2 + PC -> RE
See Also
SH3-DSP Registers | SH3-DSP General Registers | SH3-DSP Status Registers | RS, RE, and ME Control Registers | SH3-DSP System Registers | DSP Unit Registers
Last updated on Thursday, April 08, 2004
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