Hardware Reference
In-Depth Information
Tabl e 7. 2
A slice encoding - example 2
Slice Codes:
Slice Codes:
Slices
Control Code
Data Code
Descriptions
XX00 010X
00
0101
Start a new slice, map Xs to 0, set
bit 5 to 1
XXXX XX11
01
1000
Start a new slice, map Xs to 1, no
bits are set to 0
X00X XXXX
00
1000
Start a new slice, map Xs to 0, no
bits are set to 1
11XX 0XXX
01
0100
Start a new slice, map Xs to 1, set
bit 4 to 0
Tabl e 7. 3
Scan-slices obtained after decompression
Slices after performing decompression
SC1
SC2
SC3
SC4
SC5
SC6
SC7
SC8
Descriptions
0
0
0
0
0
1
0
0
Xs are set to 0
1
1
1
1
1
1
1
1
Xs are set to 1
0
0
0
0
0
0
0
0
Xs are set to 0
1
1
1
1
0
1
1
1
Xs are set to 1
6
6
6
6
5
3
6
6
T
44
Tot al W T
Tabl e 7. 4
Slice encoding with the 0-filling option
Slices
Slice Codes
0
0
0
0
0
1
0
0
00
0101
0
0
0
0
0
0
1
1
00
1000
11
0100
11
0011
0
0
0
0
0
0
0
0
00
1000
1
1
0
0
0
0
0
0
00
1000
11
0000
11
1100
15
Total WT
The scan slices obtained after decompression and applied to the internal scan
sitions (WT) in each internal scan chain (SC) and the total number of weighted
transitions generated at the circuit inputs after application of all test patterns. As can
be seen, the toggle activity in each scan chain is very high, mainly because Xs in
the scan slices are set alternatively to 0 and 1 before performing the compression
procedure.
By modifying the assignment of don't-care bits in our example, and filling all
don't care with 0 (0-filling) or 1 (1-filling) for the entire test sequence, the total num-
ber of WT is greatly reduced (15 with the 0-filling option and 19 with the 1-filling
