EP4CE55 datasheet(39/42 Pages) ALTERA

39 / 42 page

Chapter 1: Cyclone IV Device Datasheet

1–39

Glossary

May 2013

Altera Corporation

Cyclone IV Device Handbook,

Volume 3

Receiver differential input discrete resistor (external to Cyclone IV devices).

Receiver Input

Waveform

Receiver input waveform for LVDS and LVPECL differential standards:

Receiver input

skew margin

(RSKM)

High-speed I/O block: The total margin left after accounting for the sampling window and TCCS.

RSKM = (TUI – SW – TCCS) / 2.

Single-ended

voltage-

referenced I/O

Standard

The JEDEC standard for SSTl and HSTL I/O standards defines both the AC and DC input signal

values. The AC values indicate the voltage levels at which the receiver must meet its timing

specifications. The DC values indicate the voltage levels at which the final logic state of the

receiver is unambiguously defined. After the receiver input crosses the AC value, the receiver

changes to the new logic state. The new logic state is then maintained as long as the input stays

beyond the DC threshold. This approach is intended to provide predictable receiver timing in the

presence of input waveform ringing.

SW (Sampling

Window)

High-speed I/O block: The period of time during which the data must be valid to capture it

correctly. The setup and hold times determine the ideal strobe position in the sampling window.

Table 1–46. Glossary (Part 3 of 5)

Letter

Term

Definitions

Single-Ended Waveform

Differential Waveform (Mathematical Function of Positive & Negative Channel)

Positive Channel (p) = V

Negative Channel (n) = V

Ground

0 V

- n

VIH(AC)

VIH(DC)

VREF

VIL(DC)

VIL(AC)

VOH

VOL

VCCIO

VSS

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