184.108.40.206. OCT Calibration Block
The OCT calibration block can calibrate the I/O buffers located in the same GPIO-B banks only, except for DDR4 DIMM implementation. Examples:
- Non-DDR4 DIMM implementation—you can use the OCT calibration block in bank 2A to calibrate the I/O buffers in bank 2A only.
- DDR4 DIMM implementation that spans across banks 2A and 2B—you can use the OCT calibration block in either bank to calibrate the DDR4 DIMM I/O buffers in both banks.
The OCT calibration process uses the RZQ pin that is available in every GPIO-B sub-bank for series-calibrated and parallel-calibrated terminations.
- You can use the RZQ pin in one sub-bank to calibrate I/Os in the other sub-bank within the same GPIO-B bank. For example, you can use the RZQ pin in the bottom index sub-bank of bank 2B to calibrate the I/Os in the top index sub-bank of bank 2B. Both sub-bank must use the same VCCIO_PIO voltage value.
- The RZQ pin is a dual-purpose I/O pin and functions as a general-purpose I/O pin if you do not use the calibration circuit.
- The RZQ pin shares the same VCCIO_PIO supply voltage with the I/O sub-bank where the pin is located.
The OCT calibration block has an external 240 Ω reference resistor associated with it through the RZQ pin available in every sub-bank.
- Connect the RZQ pin to GND through an external 240 Ω resistor.
- For differential I/O standards, you must use the same RZQ resistor to calibrate both the positive and negative legs of the differential I/O pin.
- You can use each RZQ resistor to calibrate two RS OCT settings and one RT OCT setting for all I/O standards.
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