Altera Designing With Low-Level Primitives - Manual (Page 48)

2–26 Altera Corporation
Designing with Low-Level Primitives User Guide April 2007
Primitives
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 three ports ( oe,
bidirin, and io) are connected. Also note that all parameters are
optional.
Example 2–17 shows a VHDL example of an ALT_BIDIR_BUF
component declaration.
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 with input_termination or
output_termination .
input_termination Any legal input on-chip-termination value for the current device. This parameter
cannot 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 cannot be used along with the “
termination ” parameter.
Table 2–10. ALT_BIDIR_BUF Ports and Parameters (Part 2 of 2)
Port/Parameter Description/Value