ODT is used to terminate input signals, helping to maintain signal quality, saving board space, and reducing external component costs. ODT is available in receive mode and also in bidirectional mode when the I/O acts as an input. If ODT is not used or not available, the I/O standards may require an external termination for better signal integrity. For more information, see I/O External Termination.
ODT can be a pull-up, pull-down, differential, or Thévenin termination with both static and dynamic control available, and is set by using the I/O attribute editor in Libero SoC or by using a PDC command.
The following table lists ODT support in GPIO and HSIO.
| I/O Standards | I/O Types (Input Only) | ODT Control | ODT Type | ODT (Ω) |
|---|---|---|---|---|
| LVDS33, LVDS25 RSDS33, RSDS25, MINILVDS33, MINILVDS25, SUBLVDS33, SUBLVDS25, LVPECL33, |
GPIO, HSIO | OFF ON Dynamic |
OFF Differential |
100 |
| SSTL18I, SSTL18II | GPIO, HSIO | OFF ON Dynamic |
OFF Thévenin |
50, 75, 150 |
| SSTL15I, SST15II | GPIO, HSIO | OFF ON Dynamic |
OFF Thévenin |
20, 30, 40, 60, 120 |
| SSTL135I, SSTL135II | HSIO | OFF ON Dynamic |
OFF Thévenin |
20, 30, 40, 60, 120 |
| POD12I, POD12II | HSIO | OFF ON Dynamic | OFF Up | 34, 40, 48, 60, 120, 240 |
| HSUL12I, HSUL12II | HSIO | OFF ON Dynamic | OFF Up |
120, 240 |
| HSTL15I, HSTL15II | GPIO | OFF ON Dynamic |
OFF Differential |
50 |
| HSUL18I, HSUL18II | GPIO, HSIO | OFF ON Dynamic |
OFF Differential |
50 |
| LVCMOS25 | GPIO, HSIO | OFF ON |
OFF Down |
120, 240 |
| LVCMOS18, LVCMOS15, LVCMOS12 | GPIO, HSIO | OFF ON |
OfFF Up Down Thévenin |
60, 120, 240 |
Select ON in the ODT control to statically set to the ODT_VALUE. Select DYNAMIC to enable the ODT_VALUE when the ODT_EN pin is applied. The static ODT setting and values can be programmed by using the I/O attribute editor in Libero SoC or by using the following PDC command.
set_io –ODT <value> –ODT_VALUE <odt_value>Value can be set as ON or OFF and ODT_VALUE can be set as listed in Table 1.