The column-loading input chip (CLIC) is a conceptual integrated-circuit chip that would serve as an interface between (1) any of various sources of image data and (2) a three-dimensional analog neural network (3DANN) of the type described in "Neural-Network Modules for High-Speed Image Processing" (NPO-19881), NASA Tech Briefs, Vol. 21, No. 10 (October 1997), page 26. The overall functions of the CLIC (see Figure 1) would be to load 8-bit digital image-intensity signals from a 64 × 64 array of pixels, convert these digital signals to an array of 64 × 64 analog voltages, and couple these voltages simultaneously to all of the corresponding 64 × 64 input terminals of the 3DANN. To prevent a data-input bottleneck, the CLIC is designed to perform these functions within a 3DANN-cycle time of 250 ns. The digital-to-analog conversion would be accomplished in only about 140 ns, leaving about 110 ns for processing by the 3DANN. The CLIC is also designed to satisfy requirements of compactness and low power consumption.

As part of the design to achieve the required high speed, the digital-to-analog-conversion would be performed locally for each of the 64 × 64 inputs to the 3DANN, by use of a 64 × 64 array of multiplying digital-to-analog converters (MDACs) at the corresponding locations. The input digital image-intensity signals for the MDACs would be coupled to the MDACs in pipeline fashion, by use of row and column arrays of 8-byte shift registers (see Figure 2).

Figure 1. The CLIC Would Serve as an Input Interface, for example, to perform rastering on a sequence of digitized 64 × 64-pixel subimages from 256 × 256-pixel image source and digital-to-analog conversion for input to a 64 × 64-pixel 3DANN.

The data would be shifted into the CLIC in parallel 8 bytes corresponding to rows or columns of pixels in the source image. It would be necessary to accommodate input in row or column groups of pixels in order to enable changes in direction of rastering when a 64 × 64 array of pixels reached the edge of a larger image of which it was a part.

For input in columns, the data would be shifted in rightward from the left edge; for input in rows, the data would be shifted in downward from the top edge or upward from the bottom edge. As the data for each successive column or row of new data was shifted in, the data already in each of the shift registers in the interior of the array would be shifted rightward (for input by columns) or up or down (for input by rows), and the data in the registers in the rightmost column (in the case of column input) or in the bottom or top row (in the case of row input) would be destroyed and replaced by new data.

Figure 2. The CLIC Would Contain an Array of MDACs and shift registers. Digital signals at a basic clock rate of 32 MHz would command the shift registers to shift rightward, upward, or downward, and would control the MDACs. The input shift registers would be arranged in banks with eight-byte parallel input and output, so that all the input data for a full column of 64× 64 array could be loaded in eight clock cycles.

While the data were being shifted into the CLIC, the MDACs would continue to operate on the data from the preceding 3DANN cycle. When all the data for a 64 × 64 array of pixels had been shifted in, all MDACs would simultaneously perform analog-to-digital conversions on the current contents of their local shift registers. After a settling time of about 140 ns, the analog output voltages of the MDACs would be ready for processing by the 3DANN. During the remaining 110 ns of the cycle, these voltages would continue to be available to the 3DANN for processing, and image data for the next cycle would be shifted in.

This work was done by Tuan A. Duong of Caltech for NASA's Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

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Refer to NPO-20033

This Brief includes a Technical Support Package (TSP).
Column-loading input chip for neural-network module

(reference NPO20033) is currently available for download from the TSP library.

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