OR3C80 datasheet(18/210 Pages) AGERE

18 / 210 page

Lucent Technologies Inc.

Data Sheet

June 1999

ORCA Series 3C and 3T FPGAs

Programmable Logic Cells (continued)

In the third submode, multiplier submode, a single

PFU can affect 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 multiplicand

bits are input at KZ[1], where K7[1] is the most signifi-

cant 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 available

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:

> BA > B1

< BA < B1

≠ BA ≠ B1

A < B

> B0

A > B

< B0

A = B

≠ B0

5-5757(F)

K7[1]

K7[0]

D Q

ASWE

K4[1]

K4[0]

D Q

K3[1]

K3[0]

D Q

K2[1]

K2[0]

D Q

K1[1]

K1[0]

D Q

K6[1]

K6[0]

D Q

K5[1]

K5[0]

D Q

K0[1]

K0[0]

D Q

REGCOUT

COUT

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