
Data Sheet
February 1997
ATT3000 Series Field-Programmable Gate Arrays
8
Lucent Technologies Inc.
Configurable Logic Block 
(continued)
5A. Combinatorial Logic Option 1
 generates two functions of four 
variables each. One variable, A, must be common to both func-
tions. The second and third variables can be any choice among 
B, C, Qx, and Qy. The fourth variable can be either D or E.
5B. Combinatorial Logic Option 2
 generates any function of five 
variables: A, D, E, and two choices among B, C, Qx, Qy.
5C. Combinatorial Logic Option 3
 allows variable E to select 
between two functions of four variables: both have common 
inputs, A and D, and any choice among B, C, Qx, and Qy for 
the remaining two variables. Option 3 can then implement 
some functions of six or seven variables.
Figure 5. Combinatorial Logic Diagram
Figure 6 shows a modulo 8 binary counter with parallel 
enable. It uses one CLB of each type. The partial func-
tions of six or seven variables are implemented by 
using the input variable (.e) to dynamically select 
between two functions of four different variables. For 
the two functions of four variables each, the indepen-
dent results (F and G) may be used as data inputs to 
either flip-flop or logic block output. For the single func-
tion of five variables and merged functions of six or 
seven variables, the F and G outputs are identical. 
Symmetry of the F and G functions and the flip-flops 
allows the interchange of CLB outputs to optimize 
routing efficiencies of the networks interconnecting 
the logic and IOBs.
Figure 6. C8BCP Macro 
A
B
C
D
E
QX
QY
ANY FUNCTION
OF UP TO 4
VARIABLES
F
ANY FUNCTION
OF UP TO 4
VARIABLES
G
QY
QX
A
B
C
D
E
ANY FUNCTION
OF 5 
VARIABLES
A
B
C
D
E
QX
QY
F
G
A
B
C
D
QX
QY
A
B
C
D
E
QX
QY
F
G
ANY FUNCTION
OF UP TO 4
VARIABLES
ANY FUNCTION
OF UP TO 4
VARIABLES
M
U
X
5A
5B
5C
5-3104(F)
CLOCK
ENABLE
PARALLEL
ENABLE
CLOCK
TERMINAL
COUNT
D0
Q0
D
Q
Q1
D1
D2
Q2
D
Q
FUNCTION OF 6 VARIABLES
D
Q
FUNCTION OF 5 VARIABLES
DUAL FUNCTION OF
4 VARIABLES
5-3105(F)