5.7.1. RS OCT without Calibration in Stratix® V Devices
The Stratix® V devices support RS OCT for single-ended I/O standards. RS OCT without calibration is supported on output only.
|I/O Standard||Uncalibrated OCT (Output)|
|3.3 V LVTTL/3.3 V LVCMOS||25/50|
|2.5 V LVCMOS||25/50|
|1.8 V LVCMOS||25/50|
|1.5 V LVCMOS||25/50|
|1.2 V LVCMOS||25/50|
|SSTL-2 Class I||50|
|SSTL-2 Class II||25|
|SSTL-18 Class I||50|
|SSTL-18 Class II||25|
|SSTL-15 Class I||50|
|SSTL-15 Class II||25|
|1.8 V HSTL Class I||50|
|1.8 V HSTL Class II||25|
|1.5 V HSTL Class I||50|
|1.5 V HSTL Class II||25|
|1.2 V HSTL Class I||50|
|1.2 V HSTL Class II||25|
|Differential SSTL-2 Class I||50|
|Differential SSTL-2 Class II||25|
|Differential SSTL-18 Class I||50|
|Differential SSTL-18 Class II||25|
|Differential SSTL-15 Class I||50|
|Differential SSTL-15 Class II||25|
|Differential 1.8 V HSTL Class I||50|
|Differential 1.8 V HSTL Class II||25|
|Differential 1.5 V HSTL Class I||50|
|Differential 1.5 V HSTL Class II||25|
|Differential 1.2 V HSTL Class I||50|
|Differential 1.2 V HSTL Class II||25|
|SSTL-15||25, 34, 40, 50|
|SSTL-12||40, 60, 240|
|HSUL-12||34.3, 40, 48, 60, 80|
The following list specifies the default settings for RS OCT without calibration in the Intel® Quartus® Prime software:
- For all non-voltage-referenced, HSTL Class I, and SSTL Class I I/O standards—50 Ω.
- For HSTL Class II and SSTL Class II I/O standards—25 Ω.
Driver-impedance matching provides the I/O driver with controlled output impedance that closely matches the impedance of the transmission line. As a result, you can significantly reduce signal reflections on PCB traces.
If you select matching impedance, current strength is no longer selectable.
To use OCT for the SSTL Class I I/O standard, you must select the 50 Ω RS OCT setting, thus eliminating the external 25 Ω RS (to match the 50 Ω transmission line). For the SSTL Class II I/O standard, you must select the 25 Ω RS OCT setting (to match the 50 Ω transmission line and the near-end external 50 Ω pull-up to VTT).
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