Achronix Speedster22i User Macro Guide Uživatelský manuál stáhnout pdf (Strana 91)

Registers DFFNR

Speedster22i Macro Cell Library

AchronixSemiconductorProprietary PAGE 75

DFFNR

Negative Clock Edge D-Type Register with Asynchronous Reset

ckn

DFFNR

Figure 2-12: Logic Symbol

DFFNRisasi

ngleD‐typeregisterwith data input (d),clock (ckn), and active‐low reset(rn)

inputs and data (q) output. The active‐low reset input overrides all other inputs when it is

assertedlowandsetsthedataoutputlow.Iftheasynchronousresetinputisnotasserted,the

dataoutputissettoth

evalueonthedatainputuponthenextfallingedgeoftheclock.

Pins

Table 2-38: Pin Descriptions

Name Type Description

d Data input.

Active-low asynchronous reset input. A lo

w on rn sets the q output low

independent of the other inputs.

ckn Negative-edge clock input.

Data output. The value pr

esent on the data input is transferred to the q

output upon the falling edge of the clock if the asynchronous reset input

is high.

Parameters

Table 2-39: Parameters

Parameter Defined Values Default Value

init 1’b0

sr_assertion “unclocked”

init

Theinitparameter defines the initial value ofthe output of theDFFNRregister.Thisisthe

valuetheregistertakesupontheinitialapplicationofpowertotheFPGA.Thedefaultvalue

oftheinitparameteris1’b0.

sr_assertion

The sr_assertion param eter defines the behavior of the output when the sn set input is

asserted.Assigningthesr_assertionto“unclocked”resultsinanasychronousassertionofthe

reset signal, where the q output is set to one upon assertion of the active‐low reset signal.

Assigningthesr_assertionto“clocked”re

sultsinasynchronousassertionoftheresetsignal,

wheretheqoutputissettooneatthenextrisingedgeoftheclock.Thedefaultvalueofthe

sr_assertionparameteris“unclocked”.

input

output

1’b0, 1’b1

“unclocked”, “clocked”

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