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

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PIC16C55XFIGURE 5-4:BLOCK DIAGRAM OF RB3:RB0 PINSRBPU (1)VDDData busWR PortBWR TRISBData LatchD QCKTRIS LatchD QCK QVDDPNVSSPTTLInputBufferweakpull-upSTBufferVDDVSSI/OpinRD TRISBRD PortBLatchQ DENRB0:INTSTBufferRD Port BNote 1: TRISB = 1 enables weak pull-up if RBPU = '0'(OPTION).TABLE 5-3:PORTB FUNCTIONSName Bit # Buffer Type FunctionRB0/INT bit0 TTL/ST (1) Input/output or external interrupt input. Internal software programmableweak pull-up.RB1 bit1 TTL Input/output pin. Internal software programmable weak pull-up.RB2 bit2 TTL Input/output pin. Internal software programmable weak pull-up.RB3 bit3 TTL Input/output pin. Internal software programmable weak pull-up.RB4 bit4 TTL Input/output pin (with interrupt on change). Internal softwareprogrammable weak pull-up.RB5 bit5 TTL Input/output pin (with interrupt on change). Internal softwareprogrammable weak pull-up.RB6 bit6 TTL/ST (2) Input/output pin (with interrupt on change). Internal softwareprogrammable weak pull-up. Serial programming clock pin.RB7 bit7 TTL/ST (2) Input/output pin (with interrupt on change). Internal softwareprogrammable weak pull-up. Serial programming data pin.Legend: ST = Schmitt Trigger, TTL = TTL inputNote 1: This buffer is a Schmitt Trigger input when configured as the external interrupt.Note 2: This buffer is a Schmitt Trigger input when used in serial programming mode.TABLE 5-4:SUMMARY OF REGISTERS ASSOCIATED WITH PORTBAddress Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0Value onPORValue onAll Other Rests06h PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxxx xxxx uuuu uuuu86h TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 1111 1111 1111 111181h OPTION RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111Legend:Note:x = unknown, u = unchangedShaded bits are not used by PORTB.DS40143C-page 26 Preliminary © 1998 Microchip Technology Inc.
PIC16C55X5.3 I/O Programming Considerations5.3.1 BI-DIRECTIONAL I/O PORTSAny instruction which writes, operates internally as aread followed by a write operation. The BCF and BSFinstructions, for example, read the register into theCPU, execute the bit operation and write the result backto the register. Caution must be used when theseinstructions are applied to a port with both inputs andoutputs defined. For example, a BSF operation on bit5of PORTB will cause all eight bits of PORTB to be readinto the CPU. Then the BSF operation takes place onbit5 and PORTB is written to the output latches. Ifanother bit of PORTB is used as a bidirectional I/O pin(e.g., bit0) and it is defined as an input at this time, theinput signal present on the pin itself would be read intothe CPU and re-written to the data latch of thisparticular pin, overwriting the previous content. As longas the pin stays in the input mode, no problem occurs.However, if bit0 is switched into output mode later on,the content of the data latch may now be unknown.Reading the port register, reads the values of the portpins. Writing to the port register writes the value to theport latch. When using read modify write instructions(ex. BCF, BSF, etc.) on a port, the value of the port pinsis read, the desired operation is done to this value, andthis value is then written to the port latch.Example 5-1 shows the effect of two sequentialread-modify-write instructions (ex., BCF, BSF, etc.) onan I/O port.A pin actively outputting a Low or High should not bedriven from external devices at the same time in orderto change the level on this pin (“wired-or”, “wired-and”).The resulting high output currents may damagethe chip.EXAMPLE 5-1: READ-MODIFY-WRITEINSTRUCTIONS ON ANI/O PORT; Initial PORT settings: PORTB Inputs;; PORTB Outputs; PORTB have external pull-up and are not; connected to other circuitry;; PORT latch PORT pins; ---------- ----------BCF PORTB, 7 ; 01pp pppp 11pp ppppBCF PORTB, 6 ; 10pp pppp 11pp ppppBSF STATUS,RP0 ;BCF TRISB, 7 ; 10pp pppp 11pp ppppBCF TRISB, 6 ; 10pp pppp 10pp pppp;; Note that the user may have expected the pin; values to be 00pp pppp. The 2nd BCF caused; RB7 to be latched as the pin value (High).5.3.2 SUCCESSIVE OPERATIONS ON I/O PORTSThe actual write to an I/O port happens at the end of aninstruction cycle, whereas for reading, the data must bevalid at the beginning of the instruction cycle(Figure 5-5). Therefore, care must be exercised if awrite followed by a read operation is carried out on thesame I/O port. The sequence of instructions should besuch to allow the pin voltage to stabilize (loaddependent) before the next instruction which causesthat file to be read into the CPU is executed. Otherwise,the previous state of that pin may be read into the CPUrather than the new state. When in doubt, it is better toseparate these instructions with an NOP or anotherinstruction not accessing this I/O port.FIGURE 5-5:SUCCESSIVE I/O OPERATIONPCInstructionfetchedRB7:RB0Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4PC PC + 1 PC + 2 PC + 3MOVWF PORTBWrite toPORTBMOVF PORTB, WRead PORTBNOPNOPTPDExecuteMOVWFPORTBPort pinsampled hereExecuteMOVFPORTB, WExecuteNOPNote:This example shows write to PORTBfollowed by a read from PORTB.Note that:data setup time = (0.25 TCY - TPD)where TCY = instruction cycle andTPD = propagation delay of Q1 cycleto output valid.Therefore, at higher clock frequencies,a write followed by a read may beproblematic.© 1998 Microchip Technology Inc. Preliminary DS40143C-page 27
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 30 and 31: PIC16C55XFIGURE 6-3: TIMER0 TIMING:
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
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PIC16C55X10.5 Timing Diagrams and S
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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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PIC16C55X, EPROM-Based 8-Bit CMOS MCU Data Sheet

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