Calibrated OCT (Output)
I/O Standard
RZQ
(Ω)
R
S
(Ω)
(12)
100
25, 50
SSTL-15
240
34, 40
240
34, 40
SSTL-135
240
34, 40
SSTL-125
240
34, 40, 48, 60, 80
HSUL-12
100
25, 50
Differential SSTL-15
240
34, 40
240
34, 40
Differential SSTL-135
240
34, 40
Differential SSTL-125
240
34, 40, 48, 60, 80
Differential HSUL-12
The R
S
OCT calibration circuit compares the total impedance of the I/O buffer to the external reference
resistor connected to the
RZQ
pin and dynamically enables or disables the transistors until they match.
Calibration occurs at the end of device configuration. When the calibration circuit finds the correct impedance,
the circuit powers down and stops changing the characteristics of the drivers.
Figure 5-14: R
S
OCT with Calibration
This figure shows the R
S
as the intrinsic impedance of the output transistors.
V
CCIO
R
S
R
S
GND
Z
0
= 50 Ω
Driver
Series Termination
Receiving
Device
Related Information
On-Chip I/O Termination in Cyclone V Devices
on page 5-34
R
T
OCT with Calibration in Cyclone V Devices
The Cyclone V devices support R
T
OCT with calibration in all banks. R
T
OCT with calibration is available
only for configuration of input and bidirectional pins. Output pin configurations do not support R
T
OCT
with calibration. If you use R
T
OCT, the V
CCIO
of the bank must match the I/O standard of the pin where
you enable the R
T
OCT.
(12)
Final values are pending silicon characterization.
I/O Features in Cyclone V Devices
Altera Corporation
CV-52005
R
T
OCT with Calibration in Cyclone V Devices
5-38
2014.01.10