Altera Designing With Low-Level Primitives - Manual (Page 42)

2–20 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 five ports ( i, oe, o, io,
and iobar) are connected. Also note that all parameters are optional.
Example 2–13 shows an example of a VHDL component instantiation,
and Example 2–14 shows a Verilog HDL example of an
ALT_IOBUF_DIFF primitive instantiation.
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
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 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 with the
termination parameter.
Table 2–8. ALT_IOBUF_DIFF Ports and Parameters (Part 2 of 2)
Port/Parameter Description/Value