Browse Prior Art Database

Multiplexing Amplitude Pointer with Digital Data to Enhance Error Correction

IP.com Disclosure Number: IPCOM000077409D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Ernisse, DJ: AUTHOR [+5]

Abstract

Error correction for tape drives is typically being performed in the control unit which controls a number of tape drives. The control unit also contains the data detection circuitry. The data signal passed from each tape drive to a control unit is a limited data signal. In other words, the analog data signal has been amplified and clipped to form a signal similar to a square wave. During clipping, the amplitude information which might be used by the control unit to correct data is lost. The logic circuits shown provide a means, whereby amplitude information may be multiplexed with a data signal and passed from the tape drive to the control unit.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Multiplexing Amplitude Pointer with Digital Data to Enhance Error Correction

Error correction for tape drives is typically being performed in the control unit which controls a number of tape drives.

The control unit also contains the data detection circuitry. The data signal passed from each tape drive to a control unit is a limited data signal. In other words, the analog data signal has been amplified and clipped to form a signal similar to a square wave. During clipping, the amplitude information which might be used by the control unit to correct data is lost. The logic circuits shown provide a means, whereby amplitude information may be multiplexed with a data signal and passed from the tape drive to the control unit.

In Fig. 1, the multiplex circuit is shown which is used to combine the data signal with the pointer gate signal. Waveforms with Fig. 1 are identified by letters; the same alphabetic letters in the circuit diagram indicate the point in the diagram at which the waveform occurs. For example, the data signal is waveform A, while the pointer gate signal is waveform B, and the multiplexed output is waveform G.

The pointer gate signal contains the amplitude information. It will always rise to an up level shortly after a data transition in the data signal, if the pointer gate signal is not already at an up level. Between data transitions, the pointer gate signal will go down if the amplitude of the analog data signal is above an acceptable threshold. If the amplitude is not above the threshold, then the pointer gate signal will stay up through a transition, and an amplitude pointer pulse is multiplexed into the data signal t(1) seconds after the data transition.

The amplitude sense function is accomplished in the tape drive in less than one data transition. In other words, the amplitude of the analog data signal is checked between each data transition, to determine if the signal is above an acceptable threshold level.

The multiplex function implemented in Fig. 1 operates as follows. Latches 10 and 12, in conjunction with the input and/or gating into the generate pointer latch 14, sample the condition of the pointer gate signal B at the data transition time. If the pointer gate signal is up, the generate pointer latch 14 is set. After a t(1) second delay, the pointer send latch 16 is set providing the multiplex gate is up. Multiplex gate signal will be up if the...