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Self Calibrating Precision Timing Circuit

IP.com Disclosure Number: IPCOM000037646D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Laurer, MK: AUTHOR

Abstract

In a wire matrix printer it is necessary to tightly control the time (pulse width) during which print head drivers are turned on. A microprocessor output signal (under microcode control) initiates an analog timing (and watchdog) circuit which creates the precision pulse width.

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Self Calibrating Precision Timing Circuit

In a wire matrix printer it is necessary to tightly control the time (pulse width) during which print head drivers are turned on. A microprocessor output signal (under microcode control) initiates an analog timing (and watchdog) circuit which creates the precision pulse width.

A printer logic card which has non-volatile memory can store the accuracy of the timing circuit for that card. The accuracy (short or long pulse width) is determined and stored in the non-volatile memory by the card tester. When the printer microcode initiates the precision pulse, it will extend or shorten the pulse by the value stored in non-volatile memory by the card tester.

In Figure 1 attached, the total pulse width is PW = M + P. When the microcode pulse is corrected (brought within tolerance) by the value stored in non-volatile memory, the total pulse width is PW = M + A + P (where "A" is the adjustment (positive or negative) from non-volatile memory), as shown in Figure 2 attached.

This type of calibration is totally automated by the card tester (both measurement and storage of data in non-volatile memory) and is therefore superior to manual adjustment.

Another application of this technique is the real-time modification of the print head pulse width for specific printer modes. The pulse width can be altered by a constant (positive or negative) in this manner as required by different modes of printer operation (different paper thickness etc.)...