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OR2C04A

ORCA® Series 2 Field-Programmable Gate Arrays

Lattice Semiconductor 

ORCA Series 2 FPGAs

Data Sheet

January 2002

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

first 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 configured to operate in the memory

mode, a 16 x 2 asynchronous memory fits into an

HLUT. Both the MA and MB modes were available in

previous ORCA architectures, and each mode can be

configured in an HLUT separately. In the Series 2,

there are two new memory modes available. The first 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 configured 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 configured as a

16 x 2 RAM in one HLUT and a five-input combinatorial

logic function in the second HLUT. This can be done by

configuring 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 five. 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

four inputs each is given in Figure 4.

F5A/F5B Mode—One Five-Input Variable Function

Each HLUT can be used to implement any five-input

combinatorial function. The input ports are A[4:0] and

B[4:0], and the output ports are F0 and F3. One five or

less input function is input into A[4:0], and the second

five 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

8

independent functions of up to five inputs is shown in

Figure 5. In this case, the LUT is configured in the F5A

and F5B modes. As a variation, the LUT can do one

function of up to five input variables and two four-input

functions using F5A and F4B modes or F4A and F5B

modes.

A4

A4

HLUTA

A3

A3

QLUT3

F3

A2

A2

A1

A1

A3

A3

A2

A2

QLUT2

F2

A1

A1

A0

A0

B4

B4

HLUTB

B3

B3

QLUT1

F1

B2

B2

B1

B1

B3

B3

B2

B2

QLUT0

F0

B1

B1

B0

B0

5-2753(F).r2

Figure 4. F4 Mode—Four Functions of Four-

Input Variables

WEA

A3

A2

A1

A0

WD3

WD2

WPE

B4

B3

B2

B1

B0

A4

A3 QLUT3

A2

A1 QLUT2

A0

WD3

WD2 c0

B4

B3 QLUT1

B2

B1 QLUT0

B0

HLUTA

F3

F2

HLUTB

F0

5-2845(F).r2

Figure 5. F5 Mode—Two Functions of Five-Input

Variables

Lattice Semiconductor

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