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Verifying Noise Detection Circuit Operation for Magnetic Tape Recording Systems

IP.com Disclosure Number: IPCOM000075802D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Lutter, EP: AUTHOR [+2]

Abstract

In digital signal recording systems, such as 9-track NRZI and PE 1/2" tape systems, signals inadvertently recorded in IBG's (interblock gaps) interleaved among recorded data signals are detected for verifying that the tape has been properly recorded in accordance with interchangeability standards. An on-line test in a CPU operating via a microprogram in an I/O controller verifies the operation of such circuits in accordance with the following: Step 1 - Write a long block of data on a magnetic tape using known techniques. Tape is stopped in the downstream IBG. Step 2 - CPU channel issues a SET DIAGNOSE command with a CCW (channel control word) having the LWR (loop write-to-read) flag set to the active condition.

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Verifying Noise Detection Circuit Operation for Magnetic Tape Recording Systems

In digital signal recording systems, such as 9-track NRZI and PE 1/2" tape systems, signals inadvertently recorded in IBG's (interblock gaps) interleaved among recorded data signals are detected for verifying that the tape has been properly recorded in accordance with interchangeability standards. An on-line test in a CPU operating via a microprogram in an I/O controller verifies the operation of such circuits in accordance with the following: Step 1 - Write a long block of data on a magnetic tape using known techniques. Tape is stopped in the downstream IBG. Step 2 - CPU channel issues a SET DIAGNOSE command with a CCW (channel control word)

having the LWR (loop write-to-read) flag set to

the active condition.

COMMENT: A SET DIAGNOSE command initiates a diagnostic mode

in the tape recording system. The LWR flag sets up

a loop write-to-read

for diagnosing recording and readback circuits.

The LWR flag indicates to the I/O controller

microprograms that the

next command chained to the SET DIAGNOSE command

will be a write or erase instruction. For the present

diagnostic purposes,

a backward search file (BSF) command will be

issued for the purposes set forth below.

Step 3 - Channel issues BSF command with a second CCW. The command is chained

to SET DIAGNOSE to maintain diagnostic mode in the

tape system.

COMMENT: BSF causes the tape to move under the transducer

such that the read gap scans the Step 1 recorded

long block of data. The

microprogram in the tape system being diagnosed believes

that the tape is not being moved because of the LWR

flag and that a write/erase operation is being performed,

rather than a read (search) operation in the backward

direction. Also,

in the write operation, the tape normally moves

in the forward direction. Because of branch-on-condition

instructions lodged in the microprograms as set forth

below, the erase gap noise-detection circuits ar...