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Chapter 1: Cyclone IV Device Datasheet
1鈥�39
Glossary
December 2013
Altera Corporation
R
RL
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 鈥� SW 鈥� TCCS) / 2.
S
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鈥�46. Glossary (Part 3 of 5)
Letter
Term
Definitions
Single-Ended Waveform
Differential Waveform (Mathematical Function of Positive & Negative Channel)
Positive Channel (p) = V
IH
Negative Channel (n) = V
IL
Ground
V
ID
V
ID
0 V
V
CM
p
- n
V
ID
VIH(AC)
VIH(DC)
VREF
VIL(DC)
VIL(AC)
VOH
VOL
VCCIO
VSS