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ADSP-BF533SBBZ500 Datenblatt(PDF) 9 Page - Analog Devices |
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ADSP-BF533SBBZ500 Datenblatt(HTML) 9 Page - Analog Devices |
9 / 60 page ADSP-BF533 Rev. D | Page 9 of 60 | September 2006 • 1-D or 2-D DMA using a linked list of descriptors •2-D DMA using an array of descriptors, specifying only the base DMA address within a common page In addition to the dedicated peripheral DMA channels, there are two memory DMA channels provided for transfers between the various memories of the ADSP-BF533 processor system. This enables transfers of blocks of data between any of the memo- ries—including external SDRAM, ROM, SRAM, and flash memory—with minimal processor intervention. Memory DMA transfers can be controlled by a very flexible descriptor-based methodology or by a standard register-based autobuffer mechanism. REAL-TIME CLOCK The ADSP-BF533 processor real-time clock (RTC) provides a robust set of digital watch features, including current time, stop- watch, and alarm. The RTC is clocked by a 32.768 kHz crystal external to the ADSP-BF533 processor. The RTC peripheral has dedicated power supply pins so that it can remain powered up and clocked even when the rest of the processor is in a low power state. The RTC provides several programmable interrupt options, including interrupt per second, minute, hour, or day clock ticks, interrupt on programmable stopwatch countdown, or interrupt at a programmed alarm time. The 32.768 kHz input clock frequency is divided down to a 1 Hz signal by a prescaler. The counter function of the timer consists of four counters: a 60 second counter, a 60 minute counter, a 24 hour counter, and a 32,768 day counter. When enabled, the alarm function generates an interrupt when the output of the timer matches the programmed value in the alarm control register. There are two alarms. The first alarm is for a time of day. The second alarm is for a day and time of that day. The stopwatch function counts down from a programmed value, with one second resolution. When the stopwatch is enabled and the counter underflows, an interrupt is generated. Like other peripherals, the RTC can wake up the processor from sleep mode upon generation of any RTC wakeup event. Additionally, an RTC wakeup event can wake up the processor from deep sleep mode, and wake up the on-chip internal voltage regulator from a powered-down state. Connect RTC pins RTXI and RTXO with external components as shown in Figure 4. WATCHDOG TIMER The ADSP-BF533 processor includes a 32-bit timer that can be used to implement a software watchdog function. A software watchdog can improve system availability by forcing the proces- sor to a known state through generation of a hardware reset, nonmaskable interrupt (NMI), or general-purpose interrupt, if the timer expires before being reset by software. The program- mer initializes the count value of the timer, enables the appropriate interrupt, then enables the timer. Thereafter, the software must reload the counter before it counts to zero from the programmed value. This protects the system from remaining in an unknown state where software, which would normally reset the timer, has stopped running due to an external noise condition or software error. If configured to generate a hardware reset, the watchdog timer resets both the core and the ADSP-BF533 processor peripherals. After a reset, software can determine if the watchdog was the source of the hardware reset by interrogating a status bit in the watchdog timer control register. The timer is clocked by the system clock (SCLK), at a maximum frequency of fSCLK. TIMERS There are four general-purpose programmable timer units in the ADSP-BF533 processor. Three timers have an external pin that can be configured either as a pulse-width modulator (PWM) or timer output, as an input to clock the timer, or as a mechanism for measuring pulse-widths and periods of external events. These timers can be synchronized to an external clock input to the PF1 pin, an external clock input to the PPI_CLK pin, or to the internal SCLK. The timer units can be used in conjunction with the UART to measure the width of the pulses in the data stream to provide an autobaud detect function for a serial channel. The timers can generate interrupts to the processor core provid- ing periodic events for synchronization, either to the system clock or to a count of external signals. In addition to the three general-purpose programmable timers, a fourth timer is also provided. This extra timer is clocked by the internal processor clock and is typically used as a system tick clock for generation of operating system periodic interrupts. Figure 4. External Components for RTC RTXO C1 C2 X1 SUGGESTED COMPONENTS: X1 = ECL IPTEK E C38J (THROUGH-HOLE PACKAGE) OR EPSO N MC405 12 pF LOAD (S URFACE-MO UNT PACKAGE) C1 = 22 pF C2 = 22 pF R1 = 10 M Ω NOTE : C1 AND C2 ARE SPECIFIC TO CRYSTAL SPECI FIED FOR X1. CONTACT CRYSTAL MANUFACTURER FOR DETAILS. C1 AND C2 SPECI FI CATIO NS ASSUME BOARD TRACE CAPACITANCE OF 3 pF. RTXI R1 |
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