# AR# 6873

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## Description

Keywords: CB2CLED, CB4CLED, CB8CLED, CB16CLED, TC, CEO, Libraries Guide

Urgency: Standard

General Description:

The truth table given in the Libraries Guide for the CBxCLED modules is
incorrect. When CLR = 1, the outputs TC and CEO are not necessarily 0, as
reported in the truth table.

## Solution

Solution:

By looking at the implementation of these macros, it is seen that the CLR line
has no direct effect on either of the outputs TC or CEO.

The truth table given for these macros in the Libraries Guide is:

if CLR=1, then
TC = 0
CEO = 0

However, this is incorrect. The outputs TC and CEO are driven by the equations,
even if CLR = 1. These are:

TC = (UP * Q0 * Q1 * ... QN) + !(UP * Q0 * Q1 ... QN)
CEO = TC * CE

Thus, the proper truth table is:

if CLR = 1, then
TC = !UP
CEO = !UP * CE

For all other operations of this macro, refer to the truth table given in the
Libraries Guide.

AR# 6873
Date 10/05/2008
Status Archive
Type General Article
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