Xerox 4450 Forms Creation Manual

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Xerox 4450 Forms Creation Manual Manual pdf 65 page image

TROUBLESHOOTINGRounding variable dataAlignment problems Under certain circumstances, a form and variable data do notalign properly, even though it appears that both use the sameline spacing. This may be the result of the effects of roundingon the line spacing.As an example, construct a form with a grid unit of 13.6 cpi and9 lpi. Horizontal lines are specified at 0, 4, 7, 10, 13, 16, 19, 22,25, 28, 31, 34, 37, 40, 43, 46, 49, 52, 55, 58, 61, 64, and 67. Thedata is printed with an override line spacing of “9.”The natural assumption is that the form and the variable data lineup. However, when the variable data is merged with the form, ittends to drift up the page. The reason for this is rounding.Specifying 9 lines per inch for the variable data means that theLPS is requested to place data at approximately 33.333333 dots.The system rounds this number down to 33 dots per line.Meanwhile, in FDL, rounding does not take place until it is timeto resolve specifications for the form to a dot address.Note that variable data has a line spacing value that is computedas dots per line, and rounding is done on that value. In FDL, therounding takes place only when it is needed to resolve to a dotaddress and, therefore, might involve more than one line at atime.For example, the line drawn at 43 is assigned to scan line 1433using the following formula:(43 * 300) / 9 = 12900 / 9 = 1433.3333 or 1433The equivalent line positioning for the variable data is computedwith the following method:43 * (300 / 9) = 43 * 33 = 1419This yields an error that increases as calculation proceeds downthe page.Furthermore, in the example form, if we had drawn lines with aREPEAT EVERY 3 LINES command, the uneven dot value(33.333333 dots per line) would not have been rounded offbecause rounding would not have been performed until it wastime to resolve the specification to a dot address. The dotaddress for three lines is an even 100 dots. So, the lines for theform would be drawn at exactly 100 dots, and the variable data,on the other hand, would be using a 99-dot spacing.Avoiding imperfect alignment The best way to ensure that a form and variable data share thesame coordinate system is to define both in terms of an integralnumber of dots. It is also important to know when rounding willaffect the alignment of the variable data and the form. In theexample, the only way to make the form match the lines of datais to set the line spacing for both at 33 dots.If variable data does not line up properly with a form, and itappears that both are using the same line spacing, find out whatthe dot value is. It is most likely in such cases that the difficultyis a variation in defining the coordinate system resulting fromrounding, and is not a software problem.XEROX 4050/4090/4450/4650 LPS FORMS CREATION GUIDE 4-15