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Recovery of User Memory in an Electronic Typewriter During Power On/Off Cycles

IP.com Disclosure Number: IPCOM000062324D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Mathis, MA: AUTHOR [+3]

Abstract

When power is cycled during certain critical processes in an electronic typewriter having a memory, loss of the user document memory can occur. The possibility of this loss during a power cycle is reduced. In an electronic typewriter, certain processes cannot be interrupted due to loss of power without loss of the user document memory. For example, it is not possible to inhibit/prevent the Non-Maskable Interrupt (NMI) that occurs with a power line disturbance, such as when power is turned off or a cartridge is inserted or removed. To alert the user that a non-interruptible operation is in progress and that the machine should not be turned off, a WAIT annunciator is turned on, but the user sometimes still turns the machine off notwithstanding the WAIT annunciator being on.

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Recovery of User Memory in an Electronic Typewriter During Power On/Off Cycles

When power is cycled during certain critical processes in an electronic typewriter having a memory, loss of the user document memory can occur. The possibility of this loss during a power cycle is reduced. In an electronic typewriter, certain processes cannot be interrupted due to loss of power without loss of the user document memory. For example, it is not possible to inhibit/prevent the Non-Maskable Interrupt (NMI) that occurs with a power line disturbance, such as when power is turned off or a cartridge is inserted or removed. To alert the user that a non-interruptible operation is in progress and that the machine should not be turned off, a WAIT annunciator is turned on, but the user sometimes still turns the machine off notwithstanding the WAIT annunciator being on. To reduce the possibility of memory loss when this occurs, code is employed in a software program to recover from this situation. When the NMI is detected, the code causes user registers to be saved on the stack and the address of the stack to be saved in a non-volatile memory, such as a battery-backed memory. When power is again turned on, the initialization code recognizes that the memory could be lost. After checking to insure that the software program is in control and that the machine is in the recoverable state, the user registers will be restored from the stack and control will be passed to the software program...