Cyclone® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683375
Date 10/18/2023
Public
Document Table of Contents

5.9.3. RT OCT with Calibration in Cyclone® V Devices

The Cyclone® V devices support RT OCT with calibration in all banks. RT OCT with calibration is available only for configuration of input and bidirectional pins. Output pin configurations do not support RT OCT with calibration. If you use RT OCT, the VCCIO of the bank must match the I/O standard of the pin where you enable the RT OCT.

Table 56.  Selectable I/O Standards for RT OCT With CalibrationThis table lists the input termination settings for calibrated OCT on different I/O standards.
I/O Standard Calibrated OCT (Input)
RT (Ω) RZQ (Ω)
SSTL-2 Class I 50 100
SSTL-2 Class II 50 100
SSTL-18 Class I 50 100
SSTL-18 Class II 50 100
SSTL-15 Class I 50 100
SSTL-15 Class II 50 100
1.8 V HSTL Class I 50 100
1.8 V HSTL Class II 50 100
1.5 V HSTL Class I 50 100
1.5 V HSTL Class II 50 100
1.2 V HSTL Class I 50 100
1.2 V HSTL Class II 50 100
Differential SSTL-2 Class I 50 100
Differential SSTL-2 Class II 50 100
Differential SSTL-18 Class I 50 100
Differential SSTL-18 Class II 50 100
Differential SSTL-15 Class I 50 100
Differential SSTL-15 Class II 50 100
Differential 1.8 V HSTL Class I 50 100
Differential 1.8 V HSTL Class II 50 100
Differential 1.5 V HSTL Class I 50 100
Differential 1.5 V HSTL Class II 50 100
Differential 1.2 V HSTL Class I 50 100
Differential 1.2 V HSTL Class II 50 100
SSTL-15 20, 30, 40, 60,120 240
SSTL-135 20, 30, 40, 60, 120 240
SSTL-125 20, 30, 40, 60, 120 240
Differential SSTL-15 20, 30, 40, 60,120 240
Differential SSTL-135 20, 30, 40, 60, 120 240
Differential SSTL-125 20, 30, 40, 60, 120 240

The RT OCT calibration circuit compares the total impedance of the I/O buffer to the external resistor connected to the RZQ pin. The circuit dynamically enables or disables the transistors until the total impedance of the I/O buffer matches the external resistor.

Calibration occurs at the end of the device configuration. When the calibration circuit finds the correct impedance, the circuit powers down and stops changing the characteristics of the drivers.

Figure 86. RT OCT with Calibration