Libraries GuideChapter 3: Design Elements (ACC1 to BYPOSC)
BRLSHFT4, 8
4-, 8-Bit Barrel Shifters
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
| Macro
|
BRLSHFT4, a 4-bit barrel shifter, can rotate four inputs (I3 - I0) up to four places. The control inputs (S1 and S0) determine the number of positions, from one to four, that the data is rotated. The four outputs (O3 - O0) reflect the shifted data inputs.
BRLSHFT8, an 8-bit barrel shifter, can rotate the eight inputs (I7 - I0) up to eight places. The control inputs (S2 - S0) determine the number of positions, from one to eight, that the data is rotated. The eight outputs (O7 - O0) reflect the shifted data inputs.
Table 3_3 BRLSHFT4 Truth Table
Inputs
| Outputs
|
|---|
S1
| S0
| I0
| I1
| I2
| I3
| O0
| O1
| O2
| O3
|
|---|
0
| 0
| a
| b
| c
| d
| a
| b
| c
| d
|
0
| 1
| a
| b
| c
| d
| b
| c
| d
| a
|
1
| 0
| a
| b
| c
| d
| c
| d
| a
| b
|
1
| 1
| a
| b
| c
| d
| d
| a
| b
| c
|
Table 3_4 BRLSHFT8 Truth Table
Inputs
| Outputs
|
|---|
S2
| S1
| S0
| I0
| I1
| I2
| I3
| I4
| I5
| I6
| I7
| O0
| O1
| O2
| O3
| O4
| O5
| O6
| O7
|
|---|
0
| 0
| 0
| a
| b
| c
| d
| e
| f
| g
| h
| a
| b
| c
| d
| e
| f
| g
| h
|
0
| 0
| 1
| a
| b
| c
| d
| e
| f
| g
| h
| b
| c
| d
| e
| f
| g
| h
| a
|
0
| 1
| 0
| a
| b
| c
| d
| e
| f
| g
| h
| c
| d
| e
| f
| g
| h
| a
| b
|
0
| 1
| 1
| a
| b
| c
| d
| e
| f
| g
| h
| d
| e
| f
| g
| h
| a
| b
| c
|
1
| 0
| 0
| a
| b
| c
| d
| e
| f
| g
| h
| e
| f
| g
| h
| a
| b
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| d
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1
| 0
| 1
| a
| b
| c
| d
| e
| f
| g
| h
| f
| g
| h
| a
| b
| c
| d
| e
|
1
| 1
| 0
| a
| b
| c
| d
| e
| f
| g
| h
| g
| h
| a
| b
| c
| d
| e
| f
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1
| 1
| 1
| a
| b
| c
| d
| e
| f
| g
| h
| h
| a
| b
| c
| d
| e
| f
| g
|
Figure 3.33 BRLSHFT8 Implementation XC3000, XC4000E, XC4000X, XC5200, XC9000, Spartan, SpartanXL, Spartan2, Virtex