Altera RAM-Based Shift Register Manuel d'utilisateur télécharger pdf (Page 5)

Chapter 1: About this Megafunction 1–3

General Description

May 2013 Altera Corporation RAM-Based Shift Register (ALTSHIFT_TAPS) Megafunction User Guide

f For more information about setting the option for the distance between taps in the

MegaWizard Plug-in Manager, refer to Chapter 2, Getting Started. For information

about the

TAP_DISTANCE

parameter, refer to Chapter 3, Specifications.

Figure (a) in Figure 1–1 shows a traditional 12-word-depth shift register. Figure (b)

shows how the data in the shift register chain are being tapped at even spaces (1st,

4th, 7th, and 10th) at the output taps of the ALTSHIFT_TAPS megafunction.

Figure 1–1. Tapping Data at Certain Points of the Shift Register Chain (Note 1), (2), (3)

Notes for Figure 1–1

(1) The ALTSHIFT_TAPS megafunction depicted here has

TAP_DISTANCE

= 3 and

NUMBER_OF_TAPS

= 4.

(2) The tapped data is output to

taps[31..0]

. Note that

taps[31..0]

is a 32-bit output because it taps four words at one time. The first word from

the MSB of the taps (

taps[31..24]

) represents the first data and is followed by the 4th data, 7th data, and 10th data.

(3) The

shiftout[7..0]

word is equivalent to

taps[31..24]

1 2 3 4 5 6 7 8 9 10 ... 25 26

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Altera RAM-Based Shift Register Manuel d'utilisateur Page 5