SH7713 datasheet(166/904 Pages) RENESAS

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Section 3 DSP Operating Unit

Rev.1.50 Aug. 30, 2006 Page 126 of 860

REJ09B0288-0150

operation result. The definition of the DC bit is selected by the CS[2:0] (condition selection) bits

in DSR. The DC bit result is:

Carry or Borrow Mode: CS[2:0] = 000: The DC bit is always cleared.

Negative Value Mode: CS[2:0] = 001: Bit 31 of the operation result is loaded into the DC bit.

Zero Value Mode: CS[2:0] = 010: The DC bit is set when the operation result is zero; otherwise

it is cleared.

Overflow Mode: CS[2:0] = 011: The DC bit is always cleared.

Signed Greater Than Mode: CS[2:0] = 100: The DC bit is always cleared.

Signed Greater Than or Equal Mode: CS[2:0] = 101: The DC bit is always cleared.

The N bit always indicates the same state as the DC bit set in negative value mode by the CS[2:0]

bits. See the negative value mode part above. The Z bit always indicates the same state as the DC

bit set in zero value mode by the CS[2:0] bits. See the zero value mode part above. The V bit

always indicates the same state as the DC bit set in overflow mode by the CS[2:0] bits. See the

overflow mode part above. The GT bit always indicates the same state as the DC bit set in signed

greater than mode by the CS[2:0] bits. See the signed greater than mode part above.

3.5.7

Fixed-Point Multiply Operation

Figure 3.16 shows the multiply operation flow. Table 3.25 shows the variation of this type of

operation and table 3.26 shows the correspondence between each operand and registers. The

multiply operation of the DSP unit is single-word signed single-precision multiplication. These

operations are executed in the DSP stage, as shown in figure 3.10. The DSP stage is the same

stage as the MA stage in which memory access is performed.

If a double-precision multiply operation is needed, the CPU standard double-word multiply

instructions can be made of use.

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