NEC 16位MCU參考手冊
The 78K0R/IC3 is a 16-bit single-chip microcontroller that uses a 78K0R CPU core and incorporates peripheral functions, such as ROM/RAM, a multi-function TImer, a multi-function serial interface, an A/D converter, a programmable gain amplifier (PGA), a comparator, a real-time counter, and a watchdog TImer.
The CAT823, CAT824, and CAT825 provide basic reset and monitoring functions for the electronic systems. Each device monitors the system voltage and maintains a reset output until that voltage reaches the device’s specified trip value and then maintains the reset output active condition until the device’s internal TImer, after a minimum TImer of 140ms; toallow the systems power supply to stabilize.
This application note describes how to decode standard DTMF tones using the minimum number of external discrete components and a PIC. The two examples use a PIC which has an 8 bit TImer and either a comparator or an ADC, although it can be modified for use on a PIC which has only digital I/O. The Appendices have example code for the 16C662 (with comparator) and 16F877 (using the ADC).
As the majority of the Digital Signal Processing is done in software, little is required in the way of external signal conditioning. Software techniques are used to model the individual elements of a DTMF Decoder IC.
The MC68HC05K0 is a low cost, low pin countsingle chip microcomputer with 504 bytes of userROM and 32 bytes of RAM. The MC68HC05K0 isa member of the 68HC05K series of devices whichare available in 16-pin DIL or SOIC packages.It uses the same CPU as the other devices in the68HC05 family and has the same instructions andregisters. Additionally, the device has a 15-stagemulti-function TImer and 10 general purposebi-directional I/0 lines. A mask option is availablefor software programmable pull-downs on all ofthe I/O pins and four of the pins are capable ofgenerating interrupts.The device is ideally suited for remote-controlkeyboard applications because the pull-downs andthe interrupt drivers on the port pins allowkeyboards to be built without any externalcomponents except the keys themselves. There isno need for external pull-up or pull-down resistors,or diodes for wired-OR interrupts, as these featuresare already designed into the device.
The STWD100 watchdog TImer circuits are self-contained devices which prevent systemfailures that are caused by certain types of hardware errors (non-responding peripherals,bus contention, etc.) or software errors (bad code jump, code stuck in loop, etc.).The STWD100 watchdog TImer has an input, WDI, and an output, WDO (see Figure 2). Theinput is used to clear the internal watchdog TImer periodically within the specified timeoutperiod, twd (see Section 3: Watchdog timing). While the system is operating correctly, itperiodically toggles the watchdog input, WDI. If the system fails, the watchdog TImer is notreset, a system alert is generated and the watchdog output, WDO, is asserted (seeSection 3: Watchdog timing).The STWD100 circuit also has an enable pin, EN (see Figure 2), which can enable ordisable the watchdog functionality. The EN pin is connected to the internal pull-downresistor. The device is enabled if the EN pin is left floating.
