Patent Application
20090106509
A claim of priority is made to Korean Patent Application No. 10-2007-0106258, filed on Oct. 22, 2007, in the Korean Intellectual Property Office, the subject matter of which is hereby incorporated by reference
The present invention relates to flash memories, and more particularly, to a memory system, including control sequencers, and a method of driving the same.
In order to enhance performance, a memory controller may be designed with hard-wired logic to control instruction sequences of a flash memory. However, a hard-wired logic memory controller is complex in design, has limited extendibility, and has difficulty efficiently controlling multiple flash memories.
In order to enhance extendibility, a memory controller may be designed in firmware to control the instruction sequences of a flash memory. This method is relatively simple in design, but lower in performance.
Embodiments of the present invention provide a memory system including multiple memory devices and a host connected to the memory devices. Each of the memory devices includes a channel control sequencer. The host includes a top control sequencer that controls the channel control sequencer of each of the memory devices.
The top control sequencer and the channel control sequencers may store microcodes, decode the microcodes, and execute the decoded microcodes, respectively.
The host may further include a processor and a direct memory access (DMA). The processor generates the microcodes, and controls the top control sequencer and the memory devices using the microcodes. The DMA transfers the microcodes to the top control sequencer and the channel control sequencer of each of the memory devices.
Each of the memory devices may further include a memory, an interface block interfacing with the memory, and a DMA. The DMA transfers data of the memory to the host under control of the corresponding channel control sequencer.
The microcodes may include instructions for controlling the memories of the memory devices. Also, each of the memories may include a OneNAND™ flash memory.
Each of the memory devices may further include an error correction code (ECC) block for correcting an error in the data. Each of the memories may include a NAND flash memory.
In other embodiments of the present invention, a method of driving a memory system includes setting microcodes in a top control sequencer and multiple channel control sequencers, and executing the microcode set in the top control sequencer. The method may further include checking execution results of the microcode.
Setting the microcode in each of the top control sequencer and the channel control sequencers may include generating the microcodes; transferring the generated microcodes to the top control sequencer and the channel control sequencers, respectively; setting a top-level sequencer control register of the top control sequencer; and inputting a start address of the microcode to a current address of the top-level sequencer control register.
Executing the microcode set in the top control sequencer may include executing the microcode recorded at the current address of the top-level sequencer control register. An interrupt is generated in the top control sequencer when the current address of the top-level sequencer control register is equal to an end address of the microcode. The current address is increased when the current address of the top-level sequencer control register is not equal to the end address of the microcode.
Checking the execution results of the microcode may include, when an error occurs in the top control sequencer, reporting the error and identifying a status register of the top control sequencer.
Executing the microcode recorded at the current address of the top-level sequencer control register may include setting a microcode in each of the channel control sequencers, and executing the microcode set in each of the channel control sequencers. Executing the microcode set in each of the channel control sequencers may include checking the execution results of the microcode.
Setting the microcode in each of the channel control sequencers may include setting a sequencer control register of each of the channel control sequencers, and inputting the start address of the microcode to a current address of the channel sequencer control register.
Executing the microcode set in each of the channel control sequencers may include executing the microcode recorded at the current address of the channel sequencer control register. An interrupt is generated in the channel control sequencer when the current address of the channel sequencer control register is an end address of the microcode. The current address of the channel sequencer control register is increased when the current address of the channel sequencer control register is not the end address of the microcode.
Checking the execution results of the microcode may include, when an error occurs in any one of the channel control sequencers, reporting the error and identifying a status register of each of the channel control sequencers.
The various embodiments of the present invention reduce the load of a host processor in a memory system, including OneNAND™ and/or NAND flash memories, for example.
The embodiments of the present invention will be described with reference to the attached drawings, wherein like reference numerals refer to like parts unless otherwise specified, and in which:
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention, however, may be embodied in various different forms, and should not be construed as being limited only to the illustrated embodiments. Rather, these embodiments are provided as examples, to convey the concept of the invention to one skilled in the art. Accordingly, known processes, elements, and techniques are not described with respect to some of the embodiments of the present invention. Throughout the drawings and written description, like reference numerals will be used to refer to like or similar elements.
In order to facilitate extendibility of a memory controller and simultaneously maintain high performance, embodiments of the present invention fix, in an initial design stage, a limited number of specific operation scenarios that are expected to be frequently performed in a flash memory system. These specific operation scenarios are provided in hard-wired logic in the memory controller. Other operation scenarios control a flash memory through firmware. Thus, embodiments of the present invention can rapidly cope with changes in the flash memory system specifications (e.g., interleaving degree and read/write unit operation size) and/or the flash memory device specifications (e.g., page size and block size).
Therefore, embodiments of the present invention provide high performance with respect to anticipated operations and functionality considered in design stages, and also provide extendibility for operations and functionality not fully considered in the design stages.
Referring to
The first memory device 30 may include a first flash memory 31 (e.g., first OneNAND™ flash memory), a channel-A (Ch. A) control sequencer 32, a first interface 33, and a first device DMA 34. The second memory device 40 may include a second flash memory 41 (e.g., second OneNAND™ flash memory), a channel-B (Ch. B) control sequencer 42, a second interface 43, and a second device DMA 44.
The host processor 10 is configured to generate microcodes (μ-codes). The microcodes are instructions that control memories included in the first and second memory devices 30 and 40, respectively, of the memory system 100. The microcodes will be described in detail with reference to
The DMA 50 transfers the microcodes, which have been generated by the host processor 10, through the system bus 60 to the top control sequencer 20 and to the Ch. A and Ch. B control sequencers 32 and 42 of the first and second memory devices 30 and 40. The microcodes transferred by the DMA 50 are stored in sequencer internal memories (not shown) of the Ch. A and Ch. B control sequencers 32 and 42, respectively. The microcodes stored in the sequencer internal memories are fetched and executed by the Ch. A and Ch. B control sequencers 32 and 42.
Alternatively, the microcodes may be generated by a user. When the microcodes are generated by the user, the generated microcodes may be previously stored in the top control sequencer 20 and the channel control sequencers 32 and 42.
Sequencer control registers (not shown) in each of the Ch. A and Ch. B control sequencers 32 and 42 and the top control sequencer 20 will be described in detail with reference to
The Ch. A control sequencer 32 of the first memory device 30 executes the microcode transferred by the DMA 50. In response to the executed microcode of the Ch. A control sequencer 32, the first device DMA 34 transfers data of the first flash memory 31 through the first interface 33 to the host processor 10 via the system bus 60. Operation of the Ch. B control sequencer 42 of the second memory device 40 is similar to the operation of the Ch. A control sequencer 32 of the first memory device 30. That is, the Ch. B control sequencer 42 executes the microcode transferred by the DMA 50. In response to the executed microcode, the second device DMA 44 transfers data of the second flash memory 41 through the second interface 43 to the host processor 10 via the system bus 60.
As described above, the memory system according to the present embodiment uses the microcodes to control the memory devices equipped therein, thus making it possible to reduce the load of the host processor in the memory system. Also, when the specifications of the memory device are changed, the memory system can control the memory device with the changed specifications by modifying the microcode.
Referring to
In the example depicted in
Also, in the depicted example, the second microcode Code #2 contains address information of the system bus, the third microcode Code #3 contains write data or read & verify data, and the fourth microcode Code #4 contains read & verify mask data.
The Ch. A and Ch. B control sequencers 32 and 42 use the microcodes to control read operations, write operations, read & verify operations, and wait-for-event operations with respect to the first and second flash memories 31 and 41 of the first and second memory devices 30 and 40, respectively.
Referring to
The sequencer internal memory according to the present embodiment may include a dual-port static random access memory (SRAM), for example.
The sequencer control registers of the top control sequencer 20 and the Ch. B control sequencer 42 are configured in substantially the same manner as the sequencer control register of the Ch. A control sequencer 32, shown in
Referring to
In step 441 of
In step 443, the top control sequencer 20 sets a top-level sequencer control register. That is, the top control sequencer 20 sets the microcode received from the DMA 50 in a start address register, an end address register, a command register, and a status register of the top-level sequencer control register. In step 444, the top control sequencer 20 inputs a start address of the microcode to a current address of the top-level sequencer control register.
In step 445, the top control sequencer 20 performs a process for executing the microcode recorded at the current address of the top-level sequencer control register. That is, the top control sequencer 20 uses the microcode to control the Ch. A and Ch. B control sequencers 32 and 42. Each of the first and second memory devices 30 and 40 occupies the system bus 60 under the control of the top control sequencer 20.
The process indicated by step 445 is set forth in detail in
In step 451 of
In step 454, the Ch. A control sequencer 32 determines whether the current address of the Ch. A sequencer control register is the end address of the microcode. When the current address of the Ch. A sequencer control register is the end address of the microcode, the Ch. A control sequencer 32 generates an interrupt signal in step 456. On the other hand, when the current address of the Ch. A sequencer control register is not the end address of the microcode, the Ch. A control sequencer 32 increases the current address of the Ch. A sequencer control register in step 455 and returns to step 453.
If an error occurs in any one of Ch. A control sequencers, the Ch. A control sequencer 32 reports the error and identifies the status registers of the channel control sequencers, in step 457.
The Ch. A and Ch. B control sequencers 32 and 42 operate in parallel. Upon completion of the operations of the Ch. A and Ch. B control sequencers 32 and 42, the process returns to
If an error occurs, the top control sequencer 20 reports the error and identifies the status register of the top control sequencer, in step 449.
Referring to
The first memory device 130 includes a first NAND flash memory 131, a Ch. A control sequencer 132, a first interface 133, a first device DMA 134, and a first error correction (ECC) block 135. The second memory device 140 includes a second NAND flash memory 141, a Ch. B control sequencer 142, a second interface 143, a second device DMA 144, and a second ECC block 145. The third memory device 150 includes a third NAND flash memory 151, a Ch. C control sequencer 152, a third interface 153, a third device DMA 154, and a third ECC block 155. The fourth memory device 160 includes a fourth NAND flash memory 161, a Ch. D control sequencer 162, a fourth interface 163, a fourth device DMA 164, and a fourth ECC block 165.
Microcodes generated by the host processor 110 control memories included in the first through fourth memory devices 130 through 160 equipped in the memory system 200. The DMA 170 transfers the microcodes, which have been generated by the host processor 110, through the system bus 180 to the top control sequencer 120 and the Ch. A through Ch. D control sequencers 132, 142, 152 and 162 of the first through fourth memory devices 130, 140, 150 and 160, respectively. The microcodes transferred by the DMA 170 are stored in sequencer internal memories (not shown) of the Ch. A through Ch. D control sequencers 132, 142, 152 and 162.
The Ch. A control sequencer 132 of the first memory device 130 executes the microcode transferred by the DMA 170. In response to the executed microcode of the Ch. A control sequencer 132, the first device DMA 134 corrects an error in data of the first NAND flash memory 131 by the first ECC block 135 and transfers the resulting data through the first interface 133 to the host processor 110.
Operations of the respective control sequencers of the second through fourth memory devices 140, 150 and 160 are similar to the operation of the Ch. A control sequencer 132 of the first memory device 130. Therefore, detailed descriptions will not be repeated for conciseness.
As described above, the memory system, according to embodiments of the present invention, uses microcodes to control memory devices equipped therein, thus making it possible to reduce the load of a host processor in the memory system. Also, when specifications of the memory device are changed, the memory system can control the memory device with the changed specifications by modifying the microcodes. It is thus possible, for example, to reduce the load of the host processor in the memory system.
While the present invention has been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, it should be understood that the above embodiments are not limiting, but illustrative.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0106258 | Oct 2007 | KR | national |
