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10
Lattice Semiconductor
Data Sheet
ORCA Series 2 FPGAs
November 2006
Programmable Logic Cells (continued)
The LUT ripple mode operation offers standard arith-
metic functions, such as 4-bit adders, subtractors,
adder/subtractors, and counters. In the
ORCA
Series 2, there are two new ripple modes available. The
rst new mode is a 4 x 1 multiplier, and the second is a
4-bit comparator. These new modes offer the advan-
tages of faster speeds as well as denser logic capabili-
ties.
When the LUT is congured to operate in the memory
mode, a 16 x 2 asynchronous memory ts into an
HLUT. Both the MA and MB modes were available in
previous
ORCA architectures, and each mode can be
congured in an HLUT separately. In the Series 2,
there are two new memory modes available. The rst is
a 16 x 4 synchronous single-port memory (SSPM), and
the second is a 16 x 2 synchronous dual-port memory
(SDPM). These new modes offer easier implementa-
tion, faster speeds, denser RAMs, and a dual-port
capability that wasn’t previously offered as an option in
the ATT2Cxx/ATT2Txx families.
If the LUT is congured to operate in the ripple mode, it
cannot be used for basic combinatorial logic or memory
functions. In modes other than the ripple, SSPM, and
SDPM modes, combinations of operating modes are
possible. For example, the LUT can be congured as a
16 x 2 RAM in one HLUT and a ve-input combinatorial
logic function in the second HLUT. This can be done by
conguring HLUTA in the MA mode and HLUTB in the
F5B mode (or vice versa).
F4A/F4B Mode—Two Four-Input Functions
Each HLUT can be used to implement two four-input
combinatorial functions, but the total number of inputs
into each HLUT cannot exceed ve. The two QLUTs
within each HLUT share three inputs. In HLUTA, the
A1, A2, and A3 inputs are shared by QLUT2 and
QLUT3. Similarly, in HLUTB, the B1, B2, and B3 inputs
are shared by QLUT0 and QLUT1. The four outputs are
F0, F1, F2, and F3. The results can be routed to the
D0, D1, D2, and D3 latch/FF inputs or as an output of
the PFU. The use of the LUT for four functions of up to
F5A/F5B Mode—One Five-Input Variable Function
Each HLUT can be used to implement any ve-input
combinatorial function. The input ports are A[4:0] and
B[4:0], and the output ports are F0 and F3. One ve or
less input function is input into A[4:0], and the second
ve or less input function is input into B[4:0]. The
results are routed to the latch/FF D0 and latch/FF D3
inputs, or as a PFU output. The use of the LUT for two
independent functions of up to ve inputs is shown in
Figure 5. In this case, the LUT is congured in the F5A
and F5B modes. As a variation, the LUT can do one
function of up to ve input variables and two four-input
functions using F5A and F4B modes or F4A and F5B
modes.
5-2753(F).r2
Figure 4. F4 Mode—Four Functions of Four-
Input Variables
5-2845(F).r2
Figure 5. F5 Mode—Two Functions of Five-Input
Variables
QLUT2
A3
A2
A1
A0
A2
A1
A0
F2
QLUT3
A4
A3
A2
A1
A3
A2
A1
F3
HLUTA
QLUT0
B3
B2
B1
B0
B2
B1
B0
F0
QLUT1
B4
B3
B2
B1
B3
B2
B1
F1
HLUTB
QLUT3
QLUT2
F3
QLUT1
QLUT0
B4
B3
B2
B1
B0
F0
WEA
A3
A2
A1
A0
B4
B3
B2
B1
B0
A4
A3
A2
A1
A0
HLUTA
HLUTB
c0
WPE
WD3
WD2
WD3
WD2
F2
Select
devices
have
been
discontinued.
See
Ordering
Information
section
for
product
status.