OR4E2 datasheet(37/124 Pages) AGERE

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Lucent Technologies Inc.

Preliminary Data Sheet

December 2000

ORCA Series 4 FPGAs

Programmable Input/Output Cells (continued)

LVDS I/O

The LVDS differential pair I/O standard allows for high-speed, low-voltage swing and low-power interfaces defined

by industry standards: ANSI*/TIA/EIA†-644 and IEEE 1596.3 SSI-LVDS. The general-purpose standard is supplied

without the need for an input reference supply and uses a low switching voltage which translates to low ac power

dissipation.

The ORCA LVDS I/O provides an integrated 100

Ω matching resistor used to provide a differential voltage across

the inputs of the receiver. The on-chip integration provides termination of the LVDS receiver without the need of dis-

crete external board resistors. The user has the programmable option to enable termination per receiver pair for

point-to-point applications or, in multipoint interfaces, limit the use of termination to bused pairs. If the user chooses

to terminate any differential receiver, a single LVDS_R pin is dedicated to connect a single 100

Ω resistor to VSS,

which will provide a balance termination to all of the LVDS receiver pairs programmed to termination. See Table 20

for the LVDS termination pin location.

Table 19 provides the dc specifications for the ORCA LVDS solution.

Table 19. LVDS I/O Specifications

Table 20. LVDS Termination Pin

PIO Downlink/Uplink

Each group of four PIO have access to an input/output shift register as shown in Figure 24. This feature allows high-

speed input data to be divided down by 1/2 or 1/4, and output data can be multiplied by 2x or 4x its internal speed.

Both the input and output shift can be programmed to operate at the same time. However, the same PIO cannot be

used for both input and output shift registers at the same time.

For input shift mode, the data from INDD from the PIO is connected to the input shift register. The input data is

divided down and is returned to the routing through the INSH nodes. In 4x mode, all the INSH nodes are used. 2x

mode uses INSH4 and INSH3. Similarly, the output shift register brings data into the register from dedicated

OUTSH nodes. 4x mode uses all the OUTSH signals. However, only OUTSH2 and OUTSH1 are used for 2x mode.

* ANSI is a registered trademark of American National Standards Institute, Inc.

† EIA is a registered trademark of Electronic Industries Association.

Parameter

Min

Typical

Max

Unit

Built-in Receiver Differential Input Resistor

100

105

Ω

Receiver Input Voltage

0.0

—

2.4

Differential Input Threshold

–100

—

100

Output Common-mode Voltage

1.125

1.25

1.375

Input Common-mode Voltage

0.2

1.25

2.2

Dedicated Chip LVDS External Termination Pin (LVDS_R) Per Package

BA352

BC432

BM680

AC3

AH29

AL1

OR4E2 Datasheet(PDF) 37 Page - Agere Systems

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