Electrical computers and digital data processing systems: input/ – Interrupt processing – Programmable interrupt processing
Reexamination Certificate
1998-06-01
2001-04-03
Lee, Thomas C. (Department: 2782)
Electrical computers and digital data processing systems: input/
Interrupt processing
Programmable interrupt processing
C710S022000, C710S048000, C710S262000
Reexamination Certificate
active
06212593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to microcontrollers, and more specifically to a microcontroller having an improved buffer descriptor ring DMA unit.
2. Description of the Related Art
Specialized microcontrollers with integrated communication features are becoming particularly attractive for communications applications. A microcontroller, or an embedded controller, is uniquely suited to combining functionality onto one monolithic semiconductor substrate (i.e. chip). By embedding various communication features within a single chip, a communications microcontroller may support a wide range of communication applications.
Microcontrollers have been used for many years in many applications. A number of these applications involve communications over electronic networks, such as telephone lines, computer networks, and local and wide area networks, in both digital and analog formats. In communications applications, a microcontroller generally has a number of integrated communications peripherals in addition to the execution unit. These can be low and high speed serial ports, as well as more sophisticated communications peripherals, such as a universal serial bus (USB) interface, and high level data link control (HDLC) channels.
Further, microcontrollers that are employed in communications applications typically include secondary peripherals that remove some of the burden of transferring data from the execution unit. For example, a direct memory access (DMA) controller can directly transfer data from memory to a communications port, and vice versa, with minimal processor intervention.
One such type of direct memory access controller is a buffer descriptor ring DMA controller. A circular buffer DMA controller is a DMA controller that allows for the transfer of data from a circular buffer in memory. A buffer descriptor ring DMA controller takes this concept a step further, providing a ring in memory of buffer descriptors, as opposed to simply a circular buffer itself. That is, a ring is maintained in memory of pointers to and control variables for buffers, also located in memory, which actually contain the data to be transferred. Buffer descriptor ring DMA is especially useful in communications applications that employ “packetized” data, such as network communications and ISDN and T1 data communications applications. Buffer descriptor ring DMA has been previously implemented. One example of such an implementation is the Am79C90C-LANCE (Local Area Network Controller for Ethernet) device by Advanced Micro Devices, Inc., of Sunnyvale, Calif. Using buffer descriptor ring DMA, software executed by the microcontroller can compose packets of data for transmission over a packet style communications network, and then commission the buffer descriptor ring DMA unit to send streams of packets with little or no processor intervention.
SUMMARY OF THE INVENTION
While buffer descriptor ring DMA can provide for efficient transmission and reception of packetized communication over communications networks, historical implementations still have bus and processor overhead during certain periods. When packets are being transmitted, typical implementations allowed for an interrupt to be executed by the DMA controller at the end of every buffer. Alternatively, such an interrupt could be disabled. In a system according to the invention, not only can interrupts be enabled or disabled at the end of each buffer transmitted, but further the buffer descriptor associated with each buffer associated includes a mask bit for this interrupt. Thus, an interrupt is generated after the transmission or reception of each buffer of data dependent upon whether an interrupt on end of buffer flag in an associated buffer descriptor is true or false.
By altering the number of overall buffers which have this interrupt on end of buffer flag set or reset, the overall interrupt frequency from the buffer descriptor ring DMA unit can be reduced or increased depending on the needs of the communication protocols in the system.
REFERENCES:
patent: 3728693 (1973-04-01), Macker et al.
patent: 3757307 (1973-09-01), Cosserat et al.
patent: 5317692 (1994-05-01), Ashton et al.
patent: 5438663 (1995-08-01), Matsumoto et al.
patent: 5448702 (1995-09-01), Garcia et al.
patent: 5448743 (1995-09-01), Gulick et al.
patent: 5606559 (1997-02-01), Badger et al.
patent: 5608423 (1997-03-01), Leach
patent: 5862389 (1999-01-01), Kardach et al.
patent: 5928342 (1999-07-01), Rossum et al.
patent: 5933654 (1999-08-01), Galdun et al.
patent: 5982296 (1999-11-01), Wakasa et al.
patent: 5991831 (1999-11-01), Lee et al.
Am186™ED/EDLV Microcontrollers User's Manual, Advanced Micro Devices Corporation, © 1997, Chapter 8, pp. 1-8 and Chapter 9, pp. 1-14.
Motorola's MC68302 Integrated Multi-protocol Processor Fact Sheet, Motorola Corporation, © 1998.
Am79C90 CMOS Local Area Network Controllere For Ethernet (C-LANCE), Advanced Micro Devices Corporation, © 1998.
MC68302 Integrated Multiprotocol Processor User's Manual, Motorola Corporation, © 1995.
Maupin Patrick E.
Pham Thai H.
Advanced Micro Devices , Inc.
Akin Gump Strauss Hauer & Feld L.L.P.
Du Thuan
Lee Thomas C.
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