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# Double Pel Vector Generator

IP.com Disclosure Number: IPCOM000037358D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 32K

IBM

## Related People

Lindgren, T: AUTHOR

## Abstract

A vector generator (VG) is described which generates movement from both end points to the middle of a line segment. For short vectors there is a decrease in processing time, since vectors lie within one row boundary in memory. Note that lines and circles are made up of small vectors.

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Double Pel Vector Generator

A vector generator (VG) is described which generates movement from both end points to the middle of a line segment. For short vectors there is a decrease in processing time, since vectors lie within one row boundary in memory. Note that lines and circles are made up of small vectors.

Assume the standard constraints on a vector are 0 & DX & DY. A zero detect is employed to detect vertical movement when moving in the minus X-axis direction to give the correct relative movement. There is only one error term and its choice of increment is governed by movement in the positive X-axis direction. After a zero detect success, there should be movement in Y. A small circuit yields the correct output in the Y direction, i.e., 1 (relative movement).

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So with the addition of address lines 1 VG behaves like 2 VGs. The advantage lies clearly for short vectors. The set up time is for 1 VG and hence is small and the generation is 2 times as fast. Note that the counter is the greatest integer & DX/2 with one additional cycle (only in + X direction) if DX is odd. (See Figs. 1 and 2.)

Also, note that the technique meshes well with area fill logic and line style. It is best suited for short vectors. Also note there is no problem with wide line mode.

Control is the normal control for a VG; the only additional logic is for the -X direction (to address finish point) where X-ORs are used to insure the correct bit sequence. Finally, note that prop...