read barcode in asp net web application Increment the contents of 0x20 in Software

Maker QR Code in Software Increment the contents of 0x20

At the end of the instructions, the contents of 0x20 should have -50. It was loaded with 47, incremented three times (to get to 50) and then decremented with the result being stored in WREG, which means that the contents of 0x20 never change. Finally, the value in 0x20 (50) is complemented and incremented, producing the result -50. As with all programs presented in this chapter, I highly encourage you to change values and experiment with the instructions to help you understand exactly how they should work. I should point out that you can repeat the negation operation of the contents of le register 0x20 by double-clicking on the PC:A text on the bottom MPLAB IDE toolbar and entering 0x8 to move to the instructions before the comf instruction and then single-step through. When you return to the in nite loop statement (the goto $), you will discover that the contents of 0x20 have been turned back to the value before the rst negation (50). Along with arithmetic operations, the PIC microcontroller can also perform the bitwise logical functions AND, OR, and XOR. These instructions are available for combining the contents of a register along with the contents of w or combining the contents of w with a constant value. When 2 bits are ANDed together, the result will be 1 if both

inputs are 1. If either input is not 1, then the result will be 0. The PIC microcontroller has two AND instructions, andwf and andlw, that perform these functions. To invoke andwf, use the instruction format

where d can specify that the result of ANDing the contents of w with Register is placed into w or back into Register. andlw is invoked using the instruction format

In both AND instructions, the zero ag is set when the result of the AND operation is equal to zero. Neither the carry nor the digit carry ags are affected. You may nd it a bit confusing to discover that Microchip refers to what I call ORing bits together as inclusive ORing. In this operation, when either bit of an OR input is set (1), then the result will be set (1). There are two instructions that execute this function, iorwf (Fig. 7.29) and iorlw. iorwf is invoked using the instruction format

ORing a constant with the contents of w is accomplished by the iorlw instruction, that has the format:

In both PIC microcontroller inclusive OR instructions, the zero ag is set if the result of the operation is zero.

The last bitwise logical operation is the exclusive OR or XOR. In this operation a bit is set if a single input bit is set and the other is reset. If both inputs are at the same state (set or reset), the result will be reset. Like ANDing and ORing, XORing in the PIC microcontroller can be done with either the contents of a register being XORed with the contents of w or the contents of w are XORed with a constant. The xorwf instruction XORs the contents of a register with w and stores the result according to the value of the destination d in the format:

To XOR the contents of w with a constant and place the result back into w, the xorlw instruction (Fig. 7.30) is used:

Like ANDing and ORing, XORing will set the zero register if the result of the operation is equal to 0x00. The rotate left (rlf, Fig. 7.31) and rotate right (rrf) instructions are useful for a number of reasons. Their basic function is to move a register 1 bit to the left (upward) or to the right (downward), with the least signi cant value being loaded from the carry ag, and the most signi cant value put into the carry ag. The rlf instruction will rotate the contents of a register to the left (up) and has the format: