6–14
Chapter 6: I/O Features in the Cyclone III Device Family
Termination Scheme for I/O Standards
Voltage-Referenced I/O Standard Termination
Voltage-referenced I/O standards require an input reference voltage (VREF) and a
termination voltage (VTT). The reference voltage of the receiving device tracks the
termination voltage of the transmitting device, as shown in Figure 6–6 and Figure 6–7.
Figure 6–6. Cyclone III Device Family HSTL I/O Standard Termination
HSTL Class I
Termination
HSTL Class II
V
V
V
TT
TT
TT
50
50
50
50
External
On-Board
Termination
50
V
V
REF
REF
Transmitter
Receiver
Transmitter
Receiver
V
V
TT
V
TT
Cyclone III Device
Cyclone III Device
Family Series OCT
25
TT
Family Series OCT
50 50
50
50
50
OCT with
and without
Calibration
50
V
V
REF
REF
Transmitter
Receiver
Transmitter
Receiver
Figure 6–7. Cyclone III Device Family SSTL I/O Standard Termination
Termination
SSTL Class I
SSTL Class II
V
TT
V
V
TT
TT
50
50
50
25
50
50
External
On-Board
Termination
25
V
V
REF
REF
Transmitter
Receiver
Transmitter
Receiver
Cyclone III Device
Family Series OCT
50
Cyclone III Device
Family Series OCT
25
V
V
TT
V
TT
TT
50
50
50
50
50
OCT with
and without
Calibration
V
REF
V
REF
Transmitter
Receiver
Transmitter
Receiver
Cyclone III Device Handbook
Volume 1
December 2011 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
