METHOD FOR ACCESSING MEMORY

• US 20060262626A1
• Filed: 10/19/2005
• Published: 11/23/2006
• Est. Priority Date: 05/19/2005
• Status: Active Grant

• Current Assignee: Ememory Technology Inc.
• Original Assignee: Ememory Technology Inc.
• Inventors: Lin, Shih-Yun, Lin, Ching-Yuan, Lu, Chun-Hung, Lin, Yen-Tai, Liao, Hong-Yi
• Granted Patent: US 7,254,086 B2
• Time in Patent Office: Days
• US Class Current: 365/225.700
• CPC Class Codes: G11C 16/105 Circuits or methods for updating contents of nonvolatile memory, especially with 'security' features to ensure reliable replacement, i.e. preventing that old data is lost before new data is reliably written
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically
• CPC Class Codes: G11C 17/146 Write once memory, i.e. allowing changing of memory content by writing additional bits
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: G11C 2216/26 Floating gate memory which is adapted to be one-time programmable [OTP], e.g. containing multiple OTP blocks permitting limited update ability

Abstract

The present invention provides a method for accessing a memory. The memory contains M one-time programmable memory blocks, and each has a first memory sector and a second memory sector. The method includes: selecting a first target memory block and reading the first target memory block. The step of selecting a first target memory block is performed by comparing the second memory sectors of N one-time programmable memory blocks from M one-time programmable memory blocks by following a search rule to select the first target memory block.

Claims

1. A method for accessing a memory device, the memory device comprising at least one one-time-programmable (OTP) memory block, and each memory block comprising a first memory section and a second memory section, the method comprising:

selecting a first target memory block;

reading the first target memory block; and

if the first memory section of the first target memory block stores a first data, a predetermined value is outputted as the value stored in the first target memory block, and if the first memory section of the first target memory block stores a second data, the value stored in the second memory section of the first target memory block is outputted as the value stored in the first target memory block.

2. The method of claim 1, wherein before an OTP memory block is programmed, each memory cell of the OTP memory block stores a first logic value, and the method further comprises:

programming the second memory section of the first target memory block such that the second memory section stores the predetermined value to erase the first target memory block.

3. The method of claim 2, wherein the memory device comprises a plurality of OTP memory blocks arranged in sequence, and the method further comprises:

writing a to-be-written data to a second target memory block that is after the first target memory block, wherein if the to-be-written data corresponds to the predetermined value, program only the first memory section of the second target memory block to store the first data, and if the to-be-written data does not correspond to the predetermined value, program the second memory section of the second target memory block according to the to-be-written data.

4. The method of claim 1, wherein the memory device comprises M OTP memory blocks, and the step of selecting the first target memory block further comprises:

comparing the second memory sections of N OTP memory blocks from the M OTP memory blocks according to a search rule to select the first target memory block.

5. The method of claim 4, wherein the search rule is a sequential search or a binary search.

6. A method for accessing a memory device, the memory device comprising at least one one-time-programmable (OTP) memory block, each memory block comprising a first memory section and a second memory section, and before an OTP memory block is programmed, each memory cell of the OTP memory block storing a first logic value, the method comprising:

selecting a first target memory block; and

programming the second memory section of the first target memory block such that the second memory section stores a predetermined value to erase the first target memory block.

7. The method of claim 6, wherein the memory device comprises a plurality of OTP memory blocks arranged in sequence, and the method further comprises:

writing a to-be-written data to a second target memory block that is after the first target memory block, wherein if the to-be-written data corresponds to the predetermined value, program only the first memory section of the second target memory block to store a first data, and if the to-be-written data does not correspond to the predetermined value, program the second memory section of the second target memory block according to the to-be-written data.

8. The method of claim 6, wherein the memory device comprises M OTP memory blocks, and the step of selecting the first target memory block further comprises:

comparing the second memory sections of N OTP memory blocks from the M OTP memory blocks according to a search rule to select the first target memory block.

9. The method of claim 8, wherein the search rule is a sequential search or a binary search.

10. A method for accessing a memory device, the memory device comprising at least one one-time-programmable (OTP) memory block, each memory block comprising a first memory section and a second memory section, and before an OTP memory block is programmed, each memory cell of the OTP memory block storing a first logic value, the method comprising:

selecting a target memory block; and

writing a to-be-written data to the target memory block, wherein if the to-be-written data corresponds to a predetermined value, program only the first memory section of the target memory block to store a first data, and if the to-be-written data does not correspond to the predetermined value, program the second memory section of the target memory block according to the to-be-written data.

11. The method of claim 10, further comprising:

reading the target memory block; and

if the first memory section of the target memory block stores the first data, the predetermined value is outputted as the value stored in the target memory block, and if the first memory section of the target memory block stores a second data, the value stored in the second memory section of the target memory block is outputted as the value stored in the target memory block.

12. The method of claim 10, wherein the memory device comprises M OTP memory blocks, and the step of selecting the target memory block further comprises:

comparing the second memory sections of N OTP memory blocks from the M OTP memory blocks according to a search rule to select the target memory block.

13. The method of claim 12, wherein the search rule is a sequential search or a binary search.