Libraries GuideChapter 3: Design Elements (ACC1 to BYPOSC)
ADSU1
1-Bit Cascadable Adder/Subtracter with Carry-In and Carry-Out
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
N/A
| N/A
| N/A
| N/A
| Macro
| N/A
| N/A
| N/A
| N/A
|
When the ADD input is High, two 1-bit words (A0 and B0) are added with a carry-in (CI), producing a 1-bit output (S0) and a carry-out (CO). When the ADD input is Low, B0 is subtracted from A0, producing a result (S0) and borrow (CO). In add mode, CO represents a carry-out, and CO and CI are active-High. In subtract mode, CO represents a borrow, and CO and CI are active-Low.
Table 3_1 Add Function, ADD=1
Inputs
| Outputs
|
|---|
A0
| B0
| CI
| S0
| CO
|
|---|
0
| 0
| 0
| 0
| 0
|
0
| 1
| 0
| 1
| 0
|
1
| 0
| 0
| 1
| 0
|
1
| 1
| 0
| 0
| 1
|
0
| 0
| 1
| 1
| 0
|
0
| 1
| 1
| 0
| 1
|
1
| 0
| 1
| 0
| 1
|
1
| 1
| 1
| 1
| 1
|
Table 3_2 Subtract Function, ADD=0
Inputs
| Outputs
|
|---|
A0
| B0
| CI
| S0
| CO
|
|---|
0
| 0
| 0
| 1
| 0
|
0
| 1
| 0
| 0
| 0
|
1
| 0
| 0
| 0
| 1
|
1
| 1
| 0
| 1
| 0
|
0
| 0
| 1
| 0
| 1
|
0
| 1
| 1
| 1
| 0
|
1
| 0
| 1
| 1
| 1
|
1
| 1
| 1
| 0
| 1
|
Figure 3.15 ADSU1 Implementation XC9000