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ST90135 数据表(PDF) 77 Page - STMicroelectronics |
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ST90135 数据表(HTML) 77 Page - STMicroelectronics |
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77 / 190 page  77/190 ST90158 - RESET AND CLOCK CONTROL UNIT (RCCU) 6.5 OSCILLATOR CHARACTERISTICS The on-chip oscillator circuit uses an inverting gate circuit with tri-state output. Notes: It is recommended to place the quartz or crystal as close as possible to the ST9 to reduce the parasitic capacitance. At low temperature, frost and humidity might prevent a correct start-up of the oscillator. OSCOUT must not be used to drive external cir- cuits. When the oscillator is stopped, OSCOUT goes high impedance. In Halt mode, set by means of the HALT instruc- tion, the parallel resistor, R, is disconnected and the oscillator is disabled, forcing the internal clock, CLOCK1, to a high level, and OSCOUT to a high impedance state. To exit the HALT condition and restart the oscilla- tor, an external RESET pulse is required, having a a minimum duration of 12ms, as illustrated in Fig- ure 41 It should be noted that, if the Watchdog function is enabled, a HALT instruction will not disable the os- cillator. This to avoid stopping the Watchdog if a HALT code is executed in error. When this occurs, the CPU will be reset when the Watchdog times out or when an external reset is applied. Table 15. Oscillator Transconductance Figure 37. Crystal Oscillator Table 16. Crystal Internal Resistance( Ω) (5V Op.) Table 17. Crystal Internal Resistance( Ω) (3V Op.) Legend: CL1,CL2: Maximum Total Capacitance on pins OSCIN and OSCOUT (the value includes the external capaci- tance tied to the pin CL1 and CL2 plus the parasitic capac- itance of the board and of the device). Note: The tables are relative to the fundamental quartz crystal only (not ceramic resonator). Figure 38. Internal Oscillator Schematic Figure 39. External Clock gm Min Typ Max 5V Operation mA/V 0.77 1.5 2.4 3V Operation 0.42 0.73 1.47 OSCIN OSCOUT CL1 CL2 ST9 CRYSTAL CLOCK 1M Ω *Recommended for oscillator stability C1=C2 Freq. 56pF 47pF 33pF 22pF 5 Mhz 110 120 210 340 4 Mhz 150 200 330 510 3 Mhz 270 350 560 850 C1=C2 Freq. 56pF 47pF 33pF 22pF 5 Mhz 35 45 75 120 4 Mhz 55 70 125 195 3 Mhz 100 135 220 350 HALT OSCIN OSCOUT RIN ROUT R OSCIN OSCOUT CLOCK INPUT NC EXTERNAL CLOCK ST9 9 |
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