Tight Clock Control

Electronic News, Nov 30, 1998

The LM9830 is said by National to have tight control over system clock rates, which allows matching the scanner clock rate to the parallel port interface speed. This results in scan speeds that are as much as 4X faster than current parallel scanners. By zooming in on a subset of CCD pixels, the device can transmit an arbitrary range of pixels to speed up the scanning of smaller items such as business cards. Pixel depths of 1, 2 or 4 bits are packed into bytes for faster scans of line art and low pixel depth images.

The microstepper motor controller determines the effective vertical resolution and moves the sensor over the image at a constant speed. A PWM current-control option for the stepper motor delivers the high torque and smooth movement needed for faster scans and superior images. This feature also allows use of a less expensive motor with a lower current rating.