The Option_Reg register is a Readable and Writable register that is used to control some modules of the PIC. This register is only available from bank 1 and bank 3. The bits of the Option_Reg register as as follows:

Those bits are Readable and Writable and after a reset they will get the value '1'. They are used to set the Prescaller rate. The values it can get are:



Bit 3 - PSA: Prescaller Assignment


This bit is Readable and Writable and after a reset it will get the value 1. This bit is used to assign the prescaller to to the Watchdog timer or the Timer 0 module. The values it can get are:

• 0: The prescaller is assigned to the Timer 0 module (TMR0)
• 1: The prescaller is assigned to the Watchdog timer (WDT)


Bit 4 - TOSE: Timer 0 Source Edge Select


This bit is Readable and Writable and after a reset it will get the value 1. It is used to select the RA4/TOCKI pin clock edge (High to Low or Low to High) on which the Timer 0 will count. The values it can get are:

• 0: Increment on Low to High
• 1: Increment on High to Low


Bit 5 - T0CS: Timer 0 Clock Source Select


This bit is Readable and Writable and after a reset it will get the value 1. This bit will define the Timer 0 module clock source. It can be either the RA4/TOCKI pin or the Internal Instruction Cycle Clock (CLKO). The values it can get are:

• 0: Timer 0 clock source is the Internal instruction cycle clock (CLKO)
• 1: Timer 0 clock source is the RA4/TOCKI pin


Bit 6 - INTEDG: RB0/INT pin Interrupt Edge Select


This bit is Readable and Writable and after a reset it will get the value 1. By altering this bit, you can select the RB0/INT pin pulse edge that the RB0/INT interrupt will occur. The values it can get are:

• 0: The RB0/INT interrupt will occur on the falling edge of the RB0/INT pin
• 1: The RB0/INT interrupt will occur on the rising edge of the RB0/INT pin


Bit 7 - -RBPU: PORTB Pull-up Enable


This bit is Readable and Writable and after a reset it will get the value 1. The RB ports have an internal programmable pull-up resistor to minimize the use of external pull-up resistors when needed. This bit will enable or disable those resistors. The values it can get are:

• 0: The RB pull-up resistors are enabled
• 1: The RB pull-up resistors are disabled



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Basics       What will you need       Choosing the right PICThe MPLAB       Getting familiar with the MPLAB environment       Creating a new project       Open and close projects       Creating new files and including them in the project       Your very first assembly program       Compile a program and transfer to the PICSection 1: Beginner's theoryMemory Organization       The Data Memory Organization       The Program Memory OrganizationThe instructions       General knowledge about instructions       Value Loading Instructions       Program Flow Instructions       Mathematic Instructions       Logic Function Instructions       Bit Orientated Instructions       Byte Orientated Instructions       Miscellaneous InstructionsThe Basic Special Function Registers       The Status Register       The Option_Reg Register       The TRIS and PORT registersBeginner's PIC Tutorials       How to use our PIC Tutorials       A Pushbutton turning an LED on and off       A Simple LED Flasher       Interfacing Multiple Switches - The internal Pull-Up resistors       An LED Sequencer       Interface a Single 7seg Digit       Interface Multiple 7seg Digits       A 3-digits Decimal Counter       A Clever ButtonSection 2: Intermediate theory       Instruction Cycle Duration and Calculated Delays       The Timer Modules - Timer0       The Timer Modules - Timer1       The Timer Modules-Timer2

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Go to the discussion forum of this book



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Bit value	TMR0 Rate	WDT Rate
000	1:2	1:1
001	1:4	1:2
010	1:8	1:4
011	1:16	1:8
100	1:32	1:16
101	1:64	1:32
110	1:128	1:64
111	1:256	1:128


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