Lucent Technologies Inc.
15
Preliminary Data Sheet, Rev. 1
September 1998
ORCA Series 3 FPGAs
Programmable Logic Cells (continued)
In the third submode, multiplier submode, a single
PFU can effect an 8 x 1 bit (4 x 1 for half-ripple mode)
multiply and sum with a partial product (see Figure 8).
The multiplier bit is input at ASWE, and the multipli-
cand bits are input at KZ[1], where K7[1] is the most sig-
nificant bit (MSB). KZ[0] contains the partial product (or
other input to be summed) from a previous stage. If
ASWE is logical 1, the multiplicand is added to the par-
tial product. If ASWE is logical 0, 0 is added to the par-
tial product, which is the same as passing the partial
product. CIN/FCIN can bring the carry-in from the less
significant PFUs if the multiplicand is wider than 8 bits,
and COUT/FCOUT holds any carry-out from the multi-
plication, which may then be used as part of the prod-
uct or routed to another PFU in multiplier mode for
multiplicand width expansion.
Ripple mode’s fourth submode features equality
comparators. The functions that are explicitly avail-
able are A
> B, A
≠ B, and A < B where the value for A
is input on KZ[0], and the value for B is input on KZ[1]. A
value of 1 on the carry-out signals valid argument. For
example, a carry-out equal to 1 in AB submode indi-
cates that the value on KZ[0] is greater than or equal to
the value on KZ[1]. Conversely, the functions A < B, A +
B, and A > B are available using the same functions but
with a 0 output expected. For example, A
> B with a 0
output indicates A < B. Table 5 shows each function
and the output expected.
If larger than 8 bits, the carry-out signal can be cas-
caded using fast-carry logic to the carry-in of any adja-
cent PFU. The use of this submode could be shown
using Figure 6, except that the CIN/FCIN input for the
least significant PFU is controlled via configuration.
Key: C = configuration data.
Figure 8. Multiplier Submode
Table 5. Ripple Mode Equality Comparator
Functions and Outputs
Equality
Function
ORCA Foundry
Submode
True, if
Carry-Out Is:
A
> BA > B1
A
< BA < B1
A
≠ BA ≠ B1
A < B
A
>B0
A > B
A
< B0
A = B
A
≠ B0
5-5757(F)
K7[1]
K7[0]
+
D Q
C
DQ
1
0
K7
ASWE
K4[1]
K4[0]
+
D Q
1
0
K4
K3[1]
K3[0]
+
D Q
1
0
K3
K2[1]
K2[0]
+
D Q
1
0
K2
K1[1]
K1[0]
+
D Q
1
0
K1
K6[1]
K6[0]
+
D Q
1
0
K6
K5[1]
K5[0]
+
D Q
1
0
K5
K0[1]
K0[0]
+
D Q
1
0
K0
F7
Q7
REGCOUT
COUT
F6
Q6
F4
Q4
F3
Q3
F2
Q2
F1
Q1
F5
Q5
F0
Q0