Software management systems and methods for automotive computing devices

• US 20040221142A1
• Filed: 05/27/2004
• Published: 11/04/2004
• Est. Priority Date: 12/20/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Beckert, Richard D., Drasnin, Sharon, Radko, Ronald Otto
• Granted Patent: US 7,296,258 B2
• Time in Patent Office: Days
• US Class Current: 712/244
• CPC Class Codes: G06F 11/1441 Resetting or repowering
• CPC Class Codes: G06F 11/2015 Redundant power supplies power supply failure G06F1/30
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 12/1027 using associative or pseudo-associative address translation means, e.g. translation look-aside buffer [TLB]
• CPC Class Codes: G06F 12/122 of the least frequently used [LFU] type, e.g. with individual count value
• CPC Class Codes: G06F 2212/2022 Flash memory

Abstract

Methods and systems for operating automotive computing devices are described. In one embodiment, a small amount of static RAM (SRAM) is incorporated into an automotive computing device. The SRAM is battery-backed to provide a non-volatile memory space in which critical data, e.g. the object store, can be maintained in the event of a power loss. Circuitry is provided to ensure that the SRAM receives back up power from the battery at appropriate times. Software manages the SRAM and the other storage assembly components and makes use of virtual paging or virtual addressing techniques to keep track of where various pages, including object store pages, are stored in the system. The software knows where all of the object store pages are located so that in the event of a power loss, the page locations are known and hence the pages can be used when power is restored. The SRAM is advantageously used to maintain so-called “dirty pages” or pages that have been written to so that these pages are not lost in the event of a power interruption. Additionally, the software can also provide an orderly means by which pages in the SRAM can be written out to flash memory thereby avoiding unnecessary flash write operations which, in turn, increases the lifetime of the flash memory.

Claims

1. An automotive computing device programmed with instructions which, when executed by the device, cause the device to:

attempt to access a page that is not currently mapped in a translation look-aside buffer (TLB);

generate a TLB miss error exception;

call an exception handler to provide the handler with an opportunity to handle the exception;

determine, with the exception handler, whether the page comprises an object store page; and

if the page comprises an object store page, copy the page from device flash memory to either device DRAM or device SRAM.

2. The automotive computing device of claim 1, wherein the instructions cause the device to copy the page to DRAM if the access is a read access.

3. The automotive computing device of claim 1, wherein the instructions cause the device to copy the page to SRAM if the access is a write access.

4. The automotive computing device of claim 1, wherein the instructions cause the device to return to another exception handler with an indication that the exception was not processed if the page does not comprise an object store page.

5. The automotive computing device of claim 1, wherein the instructions cause the device to, responsive to copying the page from device flash memory to either device DRAM or device SRAM, update an object store page table in the SRAM to reflect the new location of the object store page.

6. The automotive computing device of claim 5, wherein the instructions cause the device to provide an indication in the object store page table that the object store page is dirty if the access was a write access.

7. One or more computer-readable media having computer-readable instructions thereon which, when executed by an automotive computing device, cause the computing device to:

attempt to access a page that is not currently mapped in a translation look-aside buffer (TLB);

generate a TLB miss error exception;

call an exception handler to provide the handler with an opportunity to handle the exception;

determine, with the exception handler, whether the page comprises an object store page;

if the page comprises an object store page, copy the page from device flash memory to either device DRAM or device SRAM; and

return to another exception handler with an indication that the exception was not processed if the page does not comprise an object store page.

8. In an automotive computing device, a method comprising:

generating a write exception in an attempt to write-access a page in device flash memory or device DRAM;

calling an exception handler to give the exception handler an opportunity to handle the write exception;

determining whether the page is an object store page;

if the page is an object store page, copying the page with the exception handler into device SRAM; and

updating an object store page table that is maintained in the SRAM to indicate that the page is now located in SRAM and that the page is dirty.

9. The method of claim 8 further comprising returning to another exception handler with an indication that the exception was not handled if the page is not an object store page.

10. One or more computer-readable media having computer-readable instructions thereon which, when executed by an automotive computing device, implement the method of claim 8.

11. A programmable automotive computing device programmed with instructions which, when executed by the computing device, implement the method of claim 8.