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COP8-PGMA-DS44P Datasheet(PDF) 10 Page - National Semiconductor (TI) |
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COP8-PGMA-DS44P Datasheet(HTML) 10 Page - National Semiconductor (TI) |
10 / 42 page Reset The RESET input when pulled low initializes the microcon- troller Initialization will occur whenever the RESET input is pulled low Upon initialization the data and configuration registers for ports L G and C are cleared resulting in these Ports being initialized to the TRI-STATE mode Pin G1 of the G Port is an exception (as noted below) since pin G1 is dedicated as the WATCHDOG andor Clock Monitor error output pin Port D is set high The PC PSW ICNTRL CNTRL T2CNTRL and T3CNTRL control registers are cleared The UART registers PSR ENU (except that TBMT bit is set) ENUR and ENUI are cleared The Comparator Select Register is cleared The S register is initialized to zero The Multi-Input Wakeup registers WKEN and WKEDG are cleared Wakeup register WKPND is unknown The stack pointer SP is initialized to 6F hex The device comes out of reset with both the WATCHDOG logic and the Clock Monitor detector armed with the WATCHDOG service window bits set and the Clock Monitor bit set The WATCHDOG and Clock Monitor circuits are in- hibited during reset The WATCHDOG service window bits being initialized high default to the maximum WATCHDOG service window of 64k tC clock cycles The Clock Monitor bit being initialized high will cause a Clock Monitor error follow- ing reset if the clock has not reached the minimum specified frequency at the termination of reset A Clock Monitor error will cause an active low error output on pin G1 This error output will continue until 16 tC–32 tC clock cycles following the clock frequency reaching the minimum specified value at which time the G1 output will enter the TRI-STATE mode The external RC network shown in Figure 6 should be used to ensure that the RESET pin is held low until the power supply to the chip stabilizes TLDD12864 – 7 RC l 5 c Power Supply Rise Time FIGURE 6 Recommended Reset Circuit Oscillator Circuits The chip can be driven by a clock input on the CKI input pin which can be between DC and 10 MHz The CKO output clock is on pin G7 (crystal configuration) The CKI input fre- quency is divided down by 10 to produce the instruction cycle clock (1tc) Figure 7 shows the Crystal and RC oscillator diagrams CRYSTAL OSCILLATOR CKI and CKO can be connected to make a closed loop crystal (or resonator) controlled oscillator Table A shows the component values required for various standard crystal values RC OSCILLATOR By selecting CKI as a single pin oscillator input a single pin RC oscillator circuit can be connected to it CKO is avail- able as a general purpose input andor HALT restart input Table II shows the variation in the oscillator frequencies as functions of the component (R and C) values TLDD12864 – 8 TLDD12864 – 9 FIGURE 7 Crystal and RC Oscillator Diagrams TABLE I Crystal Oscillator Configuration TA e 25 C R1 R2 C1 C2 CKI Freq Conditions (kX)(MX) (pF) (pF) (MHz) 0 1 30 30 – 36 10 VCC e 5V 0 1 30 30 – 36 4 VCC e 5V 0 1 200 100 – 150 0455 VCC e 5V TABLE II RC Oscillator Configuration TA e 25 C R C CKI Freq Instr Cycle Conditions (kX) (pF) (MHz) (ms) 33 82 22 to 27 37 to 46 VCC e 5V 56 100 11 to 13 74 to 90 VCC e 5V 68 100 09 to 11 88 to 108 VCC e 5V Note 3k s R s 200k 50 pF s C s 200 pF http www nationalcom 10 |
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