Browse Prior Art Database

Programmable Disk Error Simulator

IP.com Disclosure Number: IPCOM000042585D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Johnson, DA: AUTHOR

Abstract

Method and apparatus are provided to create simulated errors, especially for disk defect simulation in a computer system. The random and transient nature of disk media defects makes it difficult to test sections of hardware and software designed to detect, report, and handle those defects. In the present method a programmable integral pulse generator is used. The generated pulse is used in a standard technique to simulate disk media errors by interfering with the serial data link between a disk unit's read/write (R/W) electronics and a disk controller's serialization/deserialization (serdes) hardware. A typical arrangement is shown in Fig. 1 which includes disk controller 10, disk unit 50 and error simulator 100.

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Programmable Disk Error Simulator

Method and apparatus are provided to create simulated errors, especially for disk defect simulation in a computer system. The random and transient nature of disk media defects makes it difficult to test sections of hardware and software designed to detect, report, and handle those defects. In the present method a programmable integral pulse generator is used. The generated pulse is used in a standard technique to simulate disk media errors by interfering with the serial data link between a disk unit's read/write (R/W) electronics and a disk controller's serialization/deserialization (serdes) hardware. A typical arrangement is shown in Fig. 1 which includes disk controller 10, disk unit 50 and error simulator 100. The generated error pulse is redriven by a logic driver appropriate for the device interface, where one state of the driver is a high impedance state (hi-Z). The driver in this hi-Z state does not interfere with normal signal operation. In the active state, the error pulse causes the serial data to be changed, thus simulating many potential disk errors (Fig. 2). The errors can be created in the serial data link in many different ways. For present purposes the actual method (circuit) of interfering with the serial data link is not relevant. In order for the interference technique to be valid, the generated pulse must be accurately aligned with the serial R/W data. The error pulse serves to gate the error driver to interfere with the serial data. The error simulator allows accurate control of the following error parameters. 1. Sector in which the error occurs (sector-in-error). 2. Error location within a sector. 3. Error pulse width. 4. Number of consecutive errors (retry). These parameters are sufficient to control the location of the sector-in- error, the error type, and the degree of permanence of the disk error. The error simulator 100 (Fig. 3) includes a data interface 115, and error parameters are loaded via this interface into parameter registry schematically shown as registers A-H inclusive in Fig. 4. Parameter data (Fig. 5) are loaded from a parameter register 122 into a functional control register 130 when the Start Sequence bit in the control register is set. The function control registers control error simulator functions, and the definitions of bits 0-3 are shown in Fig. 6. The error simulator common card 170 (Fig. 3) is shown in detail in Fig. 7. A programmable trigger 175 defines a point in time called a "Sector Data Event" (SDE). An SDE pulse on line 176 is the combination of a sector time on the disk and the presence of a specified disk controller data operation (command). The SDE pulse is used to count from the start of a disk controller data operation to the sector in error. An SDE pulse is also used to count ERP (error recovery procedures) retry operations. An example of an SDE state for a read data command is the "ID Compare" state. In order to define an SDE, appropriat...