Altera Designing With Low-Level Primitives - Manual (Page 45)

Altera Corporation 2–23
April 2007 Designing with Low-Level Primitives User Guide
Primitive Reference
Each parameter except slew_rate also accepts the value “none”.
Assigning the value “none” to any such parameter is equivalent to not
setting the parameter. The parameter
slew_rate accepts the value –1 as
the default. Assigning –1 to slew_rate is equivalent to not setting the
parameter. Note that the primitive requires that all four ports ( oe,
bidirin, io, and iobar) are connected. Also note that all parameters
are optional. This primitive can only be used with an altddio_bidir
megafunction, and with the port connections described above; using it in
any other configuration will result in an error.
Parameter Name
io_standard Any legal differential I/O standard value.
current_strength Any legal value of the current_strength_new QSF assignment.
location Any legal pin location for the current device.
slew_rate Any legal slew rate value for the current device. This value must be a positive
integer (including 0).
enable_bus_hold Whether to enable bus-hold circuitry. Current legal values are “ on ” and “ off ”.
weak_pull_up_resistor Whether or not to enable the weak pull-up resistor. Current legal values are “ on ”
and “ off ”.
termination Any legal on-chip-termination value for the current device. This value is set as
the input as well as the output termination value for the current device. To set
separate input and output values, use the
input_termination and
output_termination parameters instead.
This parameter cannot be used along with input_termination or
output_termination .
input_termination Any legal input on-chip-termination value for the current device. This parameter
can not be used along with the “
termination ” parameter.
Note: The Fitter ignores this parameter for Cyclone III devices.
output_termination Any legal output on-chip-termination value for the current device. This
parameter can not be used along with the “
termination ” parameter.
Table 2–9. ALT_BIDIR_DIFF Ports and Parameters (Part 2 of 2)
Port/Parameter Description/Value