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

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<strong>PIC16C55X</strong>FIGURE 6-3: TIMER0 TIMING: INTERNAL CLOCK/PRESCALE 1:2PC(ProgramCounter)InstructionFetchQ1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4PC-1PC PC+1 PC+2 PC+3 PC+4 PC+5 PC+6MOVWF TMR0 MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W MOVF TMR0,WTMR0T0T0+1 NT0NT0+1InstructionExecuteWrite TMR0executedRead TMR0reads NT0Read TMR0reads NT0Read TMR0reads NT0Read TMR0reads NT0Read TMR0reads NT0 + 1FIGURE 6-4:TIMER0 INTERRUPT TIMINGQ1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4OSC1CLKOUT(3)TMR0 timerT0IF bit(INTCON)FEh1 1FFh 00h 01h 02hGIE bit(INTCON)INSTRUCTION FLOWPCInterrupt Latency TimePC PC +1 PC +1 0004h 0005hInstructionfetchedInst (PC)Inst (PC+1)Inst (0004h)Inst (0005h)InstructionexecutedInst (PC-1)Inst (PC)Dummy cycleDummy cycleInst (0004h)Note 1: T0IF interrupt flag is sampled here (every Q1).2: Interrupt latency = 4Tcy, where Tcy = instruction cycle time.3: CLKOUT is available only in RC oscillator mode.DS40143C-page 30 Preliminary © 1998 Microchip Technology Inc.
<strong>PIC16C55X</strong>6.2 Using Timer0 with External ClockWhen an external clock input is used for Timer0, it mustmeet certain requirements. The external clockrequirement is due to internal phase clock (TOSC)synchronization. Also, there is a delay in the actualincrementing of Timer0 after synchronization.6.2.1 EXTERNAL CLOCK SYNCHRONIZATIONWhen no prescaler is used, the external clock input isthe same as the prescaler output. The synchronizationof T0CKI with the internal phase clocks isaccomplished by sampling the prescaler output on theQ2 and Q4 cycles of the internal phase clocks(Figure 6-5). Therefore, it is necessary for T0CKI to behigh for at least 2TOSC (and a small RC delay of 20 ns)and low for at least 2TOSC (and a small RC delay of20 ns). Refer to the electrical specification of thedesired device.When a prescaler is used, the external clock input isdivided by the asynchronous ripple-counter typeprescaler so that the prescaler output is symmetrical.For the external clock to meet the samplingrequirement, the ripple-counter must be taken intoaccount. Therefore, it is necessary for T0CKI to have aperiod of at least 4TOSC (and a small RC delay of40 ns) divided by the prescaler value. The onlyrequirement on T0CKI high and low time is that they donot violate the minimum pulse width requirement of10 ns. Refer to parameters 40, 41 and 42 in theelectrical specification of the desired device.6.2.2 TIMER0 INCREMENT DELAYSince the prescaler output is synchronized with theinternal clocks, there is a small delay from the time theexternal clock edge occurs to the time the TMR0 isactually incremented. Figure 6-5 shows the delay fromthe external clock edge to the timer incrementing.FIGURE 6-5:TIMER0 TIMING WITH EXTERNAL CLOCKExternal Clock Input orPrescaler output (2)External Clock/PrescalerOutput after samplingIncrement Timer0 (Q4)Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4Small pulsemisses sampling(3)(1)Timer0 T0 T0 + 1 T0 + 2Note 1: Delay from clock input change to Timer0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).Therefore, the error in measuring the interval between two edges on Timer0 input = ±4Tosc max.2: External clock if no prescaler selected, Prescaler output otherwise.3: The arrows indicate the points in time where sampling occurs.© 1998 Microchip Technology Inc. Preliminary DS40143C-page 31
Page 4 and 5: PIC16C55XNOTES:DS40143C-page 4 Prel
Page 6 and 7: PIC16C55XTABLE 1-1:PIC16C55X FAMILY
Page 8 and 9: PIC16C55XNOTES:DS40143C-page 8 Prel
Page 10: PIC16C55XFIGURE 3-1: BLOCK DIAGRAMD
Page 15: PIC16C55X4.2.2 SPECIAL FUNCTION REG
Page 18 and 19: PIC16C55X4.2.2.3 INTCON REGISTERThe
Page 20 and 21: PIC16C55X4.3 PCL and PCLATHThe prog
Page 22 and 23: PIC16C55XNOTES:DS40143C-page 22 Pre
Page 24 and 25: PIC16C55XTABLE 5-1:PORTA FUNCTIONSN
Page 26 and 27: PIC16C55XFIGURE 5-4:BLOCK DIAGRAM O
Page 32 and 33: PIC16C55X6.3 PrescalerAn 8-bit coun
Page 36 and 37: PIC16C55X7.1 Configuration BitsThe
Page 38 and 39: PIC16C55X7.2.3 EXTERNAL CRYSTAL OSC
Page 40 and 41: PIC16C55X7.4 Power-on Reset (POR),
Page 42 and 43: PIC16C55XTABLE 7-5:INITIALIZATION C
Page 44 and 45: PIC16C55XFIGURE 7-11:EXTERNAL POWER
Page 46 and 47: PIC16C55X7.5.1 RB0/INT INTERRUPTAn
Page 48 and 49: PIC16C55XFIGURE 7-14:WATCHDOG TIMER
Page 50 and 51: PIC16C55X7.9 Code ProtectionIf the
Page 52 and 53: PIC16C55XTABLE 8-2:Mnemonic,Operand
Page 54 and 55: PIC16C55XBCFBit Clear fSyntax: [ la
Page 56 and 57: PIC16C55XCLRWDTSyntax:Operands:Oper
Page 58 and 59: PIC16C55XIORWFInclusive OR W with f
Page 60 and 61: PIC16C55XRETURN Return from Subrout
Page 62 and 63: PIC16C55XSWAPFSwap Nibbles in fSynt
Page 64 and 65: PIC16C55X9.6 SIMICE Entry-Level Har
Page 66 and 67: PIC16C55X9.16 KEELOQ ® Evaluation
Page 70 and 71: PIC16C55XTABLE 10-1:CROSS REFERENCE
Page 72 and 73: PIC16C55X10.2 DC CHARACTERISTICS: P
Page 74 and 75: PIC16C55X10.3 DC CHARACTERISTICS: P
Page 76 and 77: PIC16C55X10.5 Timing Diagrams and S
Page 78 and 79: PIC16C55XFIGURE 10-4:RESET, WATCHDO
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PIC16C55XNOTES:DS40143C-page 80 Pre
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PIC16C55XPackage Type:K04-010 18-Le
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PIC16C55XPackage Type:K04-051 18-Le
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PIC16C55XPrescaler ................
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PIC16C55XREADER RESPONSEIt is our i
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WORLDWIDE SALES AND SERVICEAMERICAS
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PIC16C55X, EPROM-Based 8-Bit CMOS MCU Data Sheet

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