HD6417320 RENESAS [Renesas Technology Corp], HD6417320 Datasheet - Page 190

• Manufacturer Part Number: HD6417320
• Description: Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 3 DSP Operating Unit
(1)
The DC bit indicates that carry or borrow is generated from the most significant bit of the
operation result, except the guard-bit parts. Some examples are shown in figure 3.11. This mode is
the default condition. When the input data is negative in a PABS or PNEG instruction, carry is
generated.
Rev. 3.00 Jan. 18, 2008 Page 128 of 1458
REJ09B0033-0300
Carry or Borrow Mode: CS[2:0] = B'000
Figure 3.11 DC Bit Generation Examples in Carry or Borrow Mode
+)
–)
Guard bits
0000
0000
0000 0001 0000 0000 0000 0000
Guard bits
0000
0000
0000 0000 0000 0000 0000 0000
Borrow is not detected
0000
0000
0000
0000
Carry is detected
Example 1
Example 3
1111
0000
0000
0000
1111
0000
0000
0000
Carry detecting point
Borrow detecting point
1111
0000
0000
0000
1111
0001
0001
0001
+)
(1)
–)
Guard bits
1111
0011
0011
Guard bits
0000
0000
111111111111111111111111
Carry is not detected
1111
1111
11101000 0000 0000 0000
0000
0000
Borrow is detected
Example 2
Example 4
0111
0001
0001
0001
0000
0000
0000
0000
Carry detecting point
Borrow detecting point
0000
0000
0000
0000
0000
0000
0001
0010