EP2S180F1020C4 Datasheet, PDF (466/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

On-Chip Termination
The Stratix II and Stratix II GX devices supports I/O driver on-chip series
(R_S) and parallel (R_T) termination through drive strength control for
single-ended I/Os. There are three ways to implement the R_S and (R_T) in
Stratix II and Stratix II GX devices:
■ R_S without calibration for both row I/Os and column I/Os
■ R_S with calibration only for column I/Os
■ R_T with calibration only for column I/Os
On-Chip Series Termination without Calibration
Stratix II and Stratix II GX devices support driver impedance matching to
provide the I/O driver with controlled output impedance that closely
matches the impedance of the transmission line. As a result, reflections
can be significantly reduced. Stratix II and Stratix II GX devices support
on-chip series termination for single-ended I/O standards (see
Figure 4–23). The R_S shown in Figure 4–23 is the intrinsic impedance of
transistors. The typical R_S values are 25 and 50. Once matching
impedance is selected, current drive strength is no longer selectable.
1
On-chip series termination without calibration is supported on
output pins or on the output function of bidirectional pins.
Figure 4–23. Stratix II and Stratix II GX On-Chip Series Termination without
Calibration
Stratix II Driver
Series Impedance
V_CCIO
Receiving
Device
R_S
Z_O
R_S
GND
4–28
Stratix II Device Handbook, Volume 2
Altera Corporation
January 2008