1. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 1 of 6
BILBO (Built-in Logic Block Observer) (Hobbit).
Adopting Conway-Mead partitioning approach, we re-design registers
so that they may (at different times) be a normal register, a shift reg.
(for scan path), a parallel signature analyser or an autonomous LFSR
(for test vector generation).
Can now apply Signature Analysis
methods to the combinational logic
block between 2 registers, using
SISO to get data in/out. Most of
hardware for testing is now designed
into the logic system.
Use standard Scan Path (such as
JTAG) to control and examine results
of built-in test.
BILBO A
BILBO B
COMBNL.
LOGIC
config. as t.p.g. (ALFSR)
config. as S.A.
SCAN IN
SCAN OUT
COMBNL.
LOGIC
2. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 2 of 6
Full BILBO Register:
Z1
Q
/Q
D
Q
Z2
Q
/Q
D
Q
Z
Q
/Q
D
QN
ZN-1
Q
/Q
D
QN-1
/SO
0
1
SI
B1
B2
3. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 3 of 6
Normal Register Operation (B1= B2 =1):
Acts as normal register.
Z1
Q
/Q
D
Q1
Z2
Q
/Q
D
Q2
ZNZN-1
Q
/Q
D
QN-1
Q
/Q
D
QN
4. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 4 of 6
Shift Register (Scan) Mode (B1= B2 =0):
Used either to drive {Qi} to particular values or read {Qi}, via serial
scan-path.
Q
/Q
D
Q1
Q
/Q
D
QN-1
Q
/Q
D
Q2
Q
/Q
DSI SO
QN
5. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 5 of 6
Autonomous LFSR (ALFSR) Mode (B1= 1, B2= 0):
Used to Generate Test Sequences.
Q
/Q
D
Q
/Q
D Q
/Q
D Q
/Q
D
QNQN-1Q1
Q2
6. EE4 Digital Electronics BILBO R. Scaife
I:ee4slidesolddocsBILBO.DOC edited: 09 March 2000 page 6 of 6
Multiple-Input Shift Register (MISR) mode (B1= 1, B2= 0):
Used in Signature Analyser mode to process output of combinational logic
block in response to signals generated by BILBO in ALFSR mode.
Z1 Z2
Q
ZN
/Q
D
Q1
Q
ZN-1
/Q
D
QN-1
Q
/Q
D
Q1
Q
/Q
D
Q2
