SH7713 datasheet(161/904 Pages) RENESAS

161 / 904 page

Section 3 DSP Operating Unit

Rev.1.50 Aug. 30, 2006 Page 121 of 860

REJ09B0288-0150

Example 1

Carry detecting point

Guard bits

Carry is detected

0000

1111

0000

1111

0000

1111

0000

1111

0001

0000 0001 0000 0000 0000 0000

Example 2

Carry detecting point

Guard bits

Carry is not detected

1111

0011

1111

0111

0001

0000

0011

(1)

11101000 0000 0000 0000

Example 3

Borrow detecting point

Guard bits

Borrow is not detected

0000

–)

0000

0001

0000 0000 0000 0000 0000 0000

Example 4

Borrow detecting point

Guard bits

Borrow is detected

0000

–)

0000

0001

0000

0001

0010

111111111111111111111111

Figure 3.11 DC Bit Generation Examples in Carry or Borrow Mode

Negative Value Mode: CS[2:0] = 001: The DC flag indicates the same value as the MSB of the

operation result. When the result is a negative number, the DC bit shows 1. When it is a positive

number, the DC bit shows 0. The ALU always executes 40-bit arithmetic operation, so the sign bit

to detect whether positive or negative is always got from the MSB of the operation result

regardless of the destination operand. Some examples are shown in figure 3.12.

Example 1

Sign bit

Guard bits

Negative value

1100

0000

0001

1100 0000 0000 0000 0000 0001

Example 2

Sign bit

Guard bits

Positive value

0011

0000

1000

0000

0001

0011 0000 1000 0000 0000 0001

Figure 3.12 DC Bit Generation Examples in Negative Value Mode

Zero Value Mode: CS[2:0] = 010: The DC flag indicates whether the operation result is 0 or not.

When the result is 0, the DC bit shows 1. When it is not 0, the DC bit shows 0.

Overflow Mode: CS[2:0] = 011: The DC bit indicates whether or not overflow occurs in the

result. When an operation yields a result beyond the range of the destination register, except the

SH7713 Datasheet(PDF) 161 Page - Renesas Technology Corp

SH7713 Datasheet(HTML) 161 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL