PIC16C55X, EPROM-Based 8-Bit CMOS MCU Data Sheet

PIC16C55X6.3 PrescalerAn 8-bit counter is available as a prescaler for theTimer0 module, or as a postscaler for the WatchdogTimer, respectively (Figure 6-6). For simplicity, thiscounter is being referred to as “prescaler” throughoutthis data sheet. Note that there is only one prescaleravailable which is mutually exclusive between theTimer0 module and the Watchdog Timer. Thus, aprescaler assignment for the Timer0 module meansthat there is no prescaler for the Watchdog Timer, andvice-versa.The PSA and PS2:PS0 bits (OPTION) determinethe prescaler assignment and prescale ratio.When assigned to the Timer0 module, all instructionswriting to the TMR0 register (e.g., CLRF 1, MOVWF 1,BSF 1,x....etc.) will clear the prescaler. Whenassigned to WDT, a CLRWDT instruction will clear theprescaler along with the Watchdog Timer. Theprescaler is not readable or writable.FIGURE 6-6:BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALERCLKOUT (=Fosc/4)Data BusT0CKIpin0MU1X1 0MUXSYNC2Tcy8TMR0 regT0SET0CSPSASet flag bit T0IFon OverflowWatchdogTimer01MUX8-bit Prescaler8PSA8-to-1MUXPS0 - PS2WDT Enable bit0 1M U XPSAWDTTime-outNote: T0SE, T0CS, PSA, PS0-PS2 are bits in the OPTION register.DS40143C-page 32 Preliminary © 1998 Microchip Technology Inc.