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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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SPEAR600 датащи(PDF) 63 Page - STMicroelectronics |
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SPEAR600 датащи(HTML) 63 Page - STMicroelectronics |
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63 / 97 page  SPEAr600 Timing characteristics Doc ID 16259 Rev 3 63/97 data are stable before the arrival of the DQS. To have a positive quantity the delay obtained by the DQ (maximum delay or last variation) must be less than one obtained by the DQS (minimum delay). So: t4MIN = DQS (delay)MIN - DQ (delay)MAX = (t1MIN + T ± one DLL element (a) + t2 MIN) - (T*3/4 ± one DLL element(a) + t3MAX) = t1MIN + T/4 + t2MIN ± one DLL element (a) - t3 MAX t5 can be expressed in a similar way, and can be defined as the tHOLD of the data: t5MIN = DQ (delay)MIN - DQS (delay)MAX = (T/2 + T*3/4 ± one DLL element (a) + t3 MIN) - (t1MAX + T ± one DLL element (a) + t2 MAX) = = T/4 + t3MIN - t2MAX - t1MAX ± one DLL element (a) Note: DQS (delay) is the combination of delays experienced by the DQS (data strobe) signal, DQ (delay) is the combination of delays experienced by the DQ (data) signal (both until the capture performed by the controller). 6.1.3 DDR2 command timings Figure 8. DDR2 command waveforms Figure 9. DDR2 command path For the command and control timings, we have to consider that the commands are launched on the negative edge of the clock and are captured on the next positive edge of the clock. a. The value “one DLL element” stands for the DLL accuracy, so we put ± one DLL element in the formulas. One DLL element = 15 ps in best case and 85 ps in worst case. t4 t5 CLK ADDRESS, STROBEs, and CONTROL LINES Q Q SET CLR D t2 t3 CLK ADDRESS, STROBEs, and CONTROL LINES ADDRESS, STROBEs, and CONTROL LINES CLK |
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