EP1M350 datasheet(20/86 Pages) ALTERA

20 / 86 page

Altera Corporation

Mercury Programmable Logic Device Family Data Sheet

Figure 8. Normal-Mode LE

Note (1)

Notes to Figure 8:

(1)

LEs in normal mode support register packing.

(2)

When using the carry-in in normal mode, the packed register feature is unavailable.

(3)

There are two LAB-wide clock enables per LAB in addition to LE-specific clock enables.

Arithmetic Mode

The arithmetic mode is ideal for implementing adders, accumulators, and

comparators. A LE in arithmetic mode contains four 2-input LUTs. The

first two 2-input LUTs compute two summations based on a possible

carry of 1 or 0; the other two LUTs generate carry outputs for the two

possible chains of the carry-select look-ahead (CSLA) circuitry. As shown

in Figure 9, the LAB carry-in signal selects the appropriate carry-in chain

(either carry-in0 or carry-in1). The logic level of the chain selected

in turn selects which parallel sum is generated as a combinatorial or

registered output. For example, when implementing an adder, this output

is the signal comprised of the sum data1 + data2 + carry, where carry is

or 1. The other two LUTs use the data1 and data2 signals to generate

two possible carry-out signals—one for a carry of 1 and the other for a

carry of 0. The carry-in0 signal acts as the carry select for the

carry-out0

output; carry-in1 acts as the carry select for the

carry-out1

output. LEs in arithmetic mode can drive out registered and

unregistered versions of the LUT output. Figure 9 shows a Mercury LE in

arithmetic mode.

PRN/ALDn

CLRN

4-Input

LUT

LE-Out

ENA

data1

data2

data3

data4

Carry-In from

Previous LE (2)

Registered

Output

Combinatorial

Output

LAB-Wide Clock Enable (3)

EP1M350 Datasheet(PDF) 20 Page - Altera Corporation

EP1M350 Datasheet(HTML) 20 Page - Altera Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

Datasheet Download

Link URL