Renesas SH7641 - Manual (Page 157)

Section 3 DSP Operation
Rev. 4.00 Sep. 14, 2005 Page 107 of 982
REJ09B0023-0400
5. Signed Greater Than Mode: CS[2:0] = 100
The DC bit is always cleared.
6. 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.
3.1.4 Fixed-Point Multiply Operation
Figure 3.8 shows the multiply operation flow. Table 3.5 shows the variation of this type of
operation and table 3.6 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 3.2. 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 SH-3's standard double-word multiply
instructions can be made of use.
0
Source 1 S
1 0
MAC
Ignored
S 0
0
Source 2 S
Destination
0
39 31
Guard Guard
39 31
Guard
39 31
Figure 3.8 Fixed-Point Multiply Operation Flow