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ADSP-2186MBST-266 Datasheet(PDF) 11 Page - Analog Devices |
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ADSP-2186MBST-266 Datasheet(HTML) 11 Page - Analog Devices |
11 / 40 page REV. 0 ADSP-2186M –11– CLKIN XTAL CLKOUT DSP Figure 3. External Crystal Connections RESET The RESET signal initiates a master reset of the ADSP-2186M. The RESET signal must be asserted during the power-up sequence to assure proper initialization. RESET during initial power-up must be held long enough to allow the internal clock to stabilize. If RESET is activated any time after power-up, the clock continues to run and does not require stabilization time. The power-up sequence is defined as the total time required for the crystal oscillator circuit to stabilize after a valid VDD is applied to the processor, and for the internal phase-locked loop (PLL) to lock onto the specific crystal frequency. A minimum of 2000 CLKIN cycles ensures that the PLL has locked but does not include the crystal oscillator start-up time. During this power-up sequence the RESET signal should be held low. On any subsequent resets, the RESET signal must meet the minimum pulsewidth specifi- cation, tRSP. The RESET input contains some hysteresis; however, if an RC circuit is used to generate the RESET signal, the use of an external Schmidt trigger is recommended. The master reset sets all internal stack pointers to the empty stack condition, masks all interrupts, and clears the MSTAT register. When RESET is released, if there is no pending bus request and the chip is configured for booting, the boot-loading sequence is Table II. Modes of Operation MODE D MODE C MODE B MODE A Booting Method X 0 0 0 BDMA feature is used to load the first 32 program memory words from the byte memory space. Program execution is held off until all 32 words have been loaded. Chip is configured in Full Memory Mode. 1 X 010No automatic boot operations occur. Program execution starts at external memory location 0. Chip is configured in Full Memory Mode. BDMA can still be used, but the processor does not automatically use or wait for these operations. 0100 BDMA feature is used to load the first 32 program memory words from the byte memory space. Program execution is held off until all 32 words have been loaded. Chip is configured in Host Mode. IACK has active pull-down. (REQUIRES ADDITIONAL HARDWARE). 0101IDMA feature is used to load any internal memory as desired. Program execution is held off until internal program memory location 0 is written to. Chip is configured in Host Mode. IACK has active pull-down.1 1100 BDMA feature is used to load the first 32 program memory words from the byte memory space. Program execution is held off until all 32 words have been loaded. Chip is configured in Host Mode; IACK requires exter- nal pull down. (REQUIRES ADDITIONAL HARDWARE) 1101IDMA feature is used to load any internal memory as desired. Program execution is held off until internal program memory location 0 is written to. Chip is configured in Host Mode. IACK requires external pull-down.1 NOTE 1Considered as standard operating settings. Using these configurations allows for easier design and better memory management. performed. The first instruction is fetched from on-chip pro- gram memory location 0x0000 once boot loading completes. Power Supplies The ADSP-2186M has separate power supply connections for the internal (VDDINT) and external (VDDEXT) power supplies. The internal supply must meet the 2.5 V requirement. The external supply can be connected to either a 2.5 V or 3.3 V supply. All external supply pins must be connected to the same supply. All input and I/O pins can tolerate input voltages up to 3.6 V, regardless of the external supply voltage. This feature provides maximum flexibility in mixing 2.5 V and 3.3 V components. MODES OF OPERATION Setting Memory Mode Memory Mode selection for the ADSP-2186M is made during chip reset through the use of the Mode C pin. This pin is multi- plexed with the DSP’s PF2 pin, so care must be taken in how the mode selection is made. The two methods for selecting the value of Mode C are active and passive. Passive Configuration Passive Configuration involves the use a pull-up or pull-down resistor connected to the Mode C pin. To minimize power con- sumption, or if the PF2 pin is to be used as an output in the DSP application, a weak pull-up or pull-down, on the order of 10 k Ω, can be used. This value should be sufficient to pull the pin to the desired level and still allow the pin to operate as a programmable flag output without undue strain on the processor’s output driver. For minimum power consumption during power-down, recon- figure PF2 to be an input, as the pull-up or pull-down will hold the pin in a known state, and will not switch. |
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