Altera Designing With Low-Level Primitives Manuel d'utilisateur télécharger pdf (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

1 2 ... 40 41 42 43 44 45 46 47 48 49 50 ... 55 56

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Altera Designing With Low-Level Primitives Manuel d'utilisateur Page 45

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