Lessons
2012 Microchip Technology Inc. DS41628B-page 51
3.4 LESSON 3: ROTATE
3.4.1 Introduction
Rotate the lit LED between the four available LEDs.
3.4.2 Hardware Effects
LEDs rotate from right to left.
3.4.3 Summary
This lesson will introduce shifting instructions as well as bit-oriented skip operations to
move the LED display.
3.4.4 New Registers
3.4.4.0.1 BOTH
3.4.4.0.2 STATUS
The STATUS register is automatically updated in hardware after every arithmetic
operation. This is used to check for the following conditions:
1. Zero
2. Digit Carry
3. Carry
4. Overflow
5. Negative
The Instruction Set Summary section in each PIC
microcontroller data sheet will indi-
cate what instructions affect which bit(s).
3.4.5 New Instructions
3.4.5.1 BOTH
3.4.5.1.1 BTFSC
This tests a specific bit in a specific register. If it is clear (value of ‘0’), then the next
instruction is skipped. This is useful for performing IF-ELSE statements.
TABLE 3-7: NEW REGISTERS FOR BOTH DEVICES
Register Purpose
STATUS Used to check ALU status
TABLE 3-8: NEW INSTRUCTIONS FOR BOTH DEVICES
Instruction English Purpose
btfsc Skip next line if bit is clear If/Else statements
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