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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) |
---|---|
RS (Ω) | |
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-135 | 34, 40 |
SSTL-125 | 34, 40 |
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).