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ADSP-21992BBC Datasheet(PDF) 7 Page - Analog Devices |
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ADSP-21992BBC Datasheet(HTML) 7 Page - Analog Devices |
7 / 60 page ADSP-21992 Rev. A | Page 7 of 60 | August 2007 The ADSP-21992 will halt program execution if the bus is granted to an external device and an instruction fetch or data read/write request is made to external general-purpose or peripheral memory spaces. If an instruction requires two exter- nal memory read accesses, the bus will not be granted between the two accesses. If an instruction requires an external memory read and an external memory write access, the bus may be granted between the two accesses. The external memory inter- face can be configured so that the core will have exclusive use of the interface. DMA and bus requests will be granted. When the external device releases BR, the DSP releases BG and continues program execution from the point at which it stopped. The bus request feature operates at all times, even while the DSP is booting and RESET is active. The ADSP-21992 asserts the BGH pin when it is ready to start another external port access, but is held off because the bus was previously granted. This mechanism can be extended to define more complex arbitration protocols for implementing more elaborate multimaster systems. DMA CONTROLLER The ADSP-21992 has a DMA controller that supports auto- mated data transfers with minimal overhead for the DSP core. Cycle stealing DMA transfers can occur between the ADSP-21992 internal memory and any of its DMA capable peripherals. Additionally, DMA transfers can be accomplished between any of the DMA capable peripherals and external devices connected to the external memory interface. DMA capable peripherals include the SPORT and SPI ports, and ADC control module. Each individual DMA capable peripheral has a dedicated DMA channel. To describe each DMA sequence, the DMA controller uses a set of parameters—called a DMA descriptor. When successive DMA sequences are needed, these DMA descriptors can be linked or chained together, so the com- pletion of one DMA sequence autoinitiates and starts the next sequence. DMA sequences do not contend for bus access with the DSP core, instead DMAs “steal” cycles to access memory. All DMA transfers use the DMA bus shown in Figure 2 on Page 4. Because all of the peripherals use the same bus, arbitra- tion for DMA bus access is needed. The arbitration for DMA bus access appears in Table 1. DSP PERIPHERALS ARCHITECTURE The ADSP-21992 contains a number of special purpose, embed- ded control peripherals, which can be seen in the functional block diagram on Page 1. The ADSP-21992 contains a high per- formance, 8-channel, 14-bit ADC system with dual-channel simultaneous sampling ability across four pairs of inputs. An internal precision voltage reference is also available as part of the ADC system. In addition, a 3-phase, 16-bit, center-based PWM generation unit can be used to produce high accuracy PWM signals with minimal processor overhead. The ADSP-21992 also contains a flexible incremental encoder inter- face unit for position sensor feedback; two adjustable frequency auxiliary PWM outputs, 16 lines of digital I/O; a 16-bit watch- dog timer; three general-purpose timers, and an interrupt controller that manages all peripheral interrupts. Finally, the ADSP-21992 contains an integrated power-on-reset (POR) cir- cuit that can be used to generate the required reset signal for device power-on. The ADSP-21992 has an external memory interface that is shared by the DSP core, the DMA controller, and DMA capable peripherals, which include the ADC, SPORT, and SPI commu- nication ports. The external port consists of a 16-bit data bus, a 20-bit address bus, and control signals. The data bus is config- urable to provide an 8- or 16-bit interface to external memory. Support for word packing lets the DSP access 16- or 24-bit words from external memory regardless of the external data bus width. The memory DMA controller lets the ADSP-21992 move data and instructions from between memory spaces: internal-to- external, internal-to-internal, and external-to-external. On-chip peripherals can also use this controller for DMA transfers. The embedded SHARC core can respond to up to 17 interrupts at any given time: three internal (stack, emulator kernel, and power-down), two external (emulator and reset), and 12 user- defined (peripherals) interrupts. Programmers assign each of the 32 peripheral interrupt requests to one of the 12 user- defined interrupts. These assignments determine the priority of each peripheral for interrupt service. The following sections provide a functional overview of the ADSP-21992 peripherals. SERIAL PERIPHERAL INTERFACE (SPI) PORT The serial peripheral interface (SPI) port provides functionality for a generic configurable serial port interface based on the SPI standard, which enables the DSP to communicate with multiple SPI-compatible devices. Key features of the SPI port are: • Interface to host microcontroller or serial EEPROM. • Master or slave operation (3-wire interface MISO, MOSI, SCK). • Data rates to HCLK 4 (16-bit baud rate selector). • 8- or 16-bit transfer. • Programmable clock phase and polarity. • Broadcast Mode–1 master, multiple slaves. • DMA capability and dedicated interrupts. Table 1. I/O Bus Arbitration Priority DMA Bus Master Arbitration Priority SPORT Receive DMA 0—Highest SPORT Transmit DMA 1 ADC Control DMA 2 SPI Receive/Transmit DMA 3 Memory DMA 4—Lowest |
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