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1. #HOW TO MULTIPLY BYTES IN CODEVISIONAVR HOW TO#
2. #HOW TO MULTIPLY BYTES IN CODEVISIONAVR CODE#
3. #HOW TO MULTIPLY BYTES IN CODEVISIONAVR SERIES#
4. #HOW TO MULTIPLY BYTES IN CODEVISIONAVR MAC#

The first example shows an assembly code that reads the port B input value and multiplies this value with a constant (5) before storing the result in register pair R17:R16. Figure 1 shows the valid (operand) register usage for each of the multiply instructions. However, note that only the MUL instruction does not have register usage restrictions.

The result will be placed in register pair R0:R1. Just load the operands into two registers (or only one for square multiply) and execute one of the multiply instructions. Performance Summary 8-bit x 8-bit Routines Word (Cycles) Unsigned multiply 8 x 8 = 16 bits 1 (2) Signed multiply 8 x 8 = 16 bits 1 (2) Fractional signed/unsigned multiply 8 x 8 = 16 bits 1 (2) Fractional signed multiply-accumulate 8 x 8 = 16 bits 3 (4) 16-bit x 16-bit Routines Signed/unsigned multiply 16 x 16 = 16 bits 6 (9) Unsigned multiply 16 x 16 = 32 bits 13 (17) Signed multiply 16 x 16 = 32 bits 15 (19) Signed multiply-accumulate 16 x 16 = 32 bits 19 (23) Fractional signed multiply 16 x 16 = 32 bits 16 (20) Fractional signed multiply-accumulate 16 x 16 = 32 bits 21 (25) Unsigned multiply 16 x 16 = 24 bits 10 (14) Signed multiply 16 x 16 = 24 bits 10 (14) Signed multiply-accumulate 16 x 16 = 24 bits 12 (16) 8-bit Multiplication Example 1 Basic Usage Doing an 8-bit multiply using the hardware multiplier is simple, as the examples in this section will clearly show. A listing of all implementations with key performance specifications is given in Table 1. The file AVR201.asm contains the application note source code of the 16-bit multiply routines. One improvement that is particularly useful is the new instruction MOVW - Copy Register Word, which makes a copy of one register pair into another register pair. 1Ģ In addition to the new multiplication instruction, a few other additions and improvements are made to the megaavr processor core. 8-bit Microcontroller Application Note Rev. The final section presents some issues regarding the use of fractional numbers.

One solution often used to solve this problem is to introduce fractional numbers, i.e., numbers that are less than 1 and greater than or equal to -1. When adding multiple values to one result variable, even when adding positive and negative values to some extent cancel each other, the risk of the result variable to OverRun its limits becomes evident, i.e., if adding one to a signed byte variable that contains the value 127, the result will be -128 instead of 128. The Multiply-Accumulate operation (sometimes referred to as multiply-add operation) has one critical drawback.

#HOW TO MULTIPLY BYTES IN CODEVISIONAVR MAC#

This application note will therefore include examples of implementing the MAC operation. The megaavr microcontrollers are designed to give the AVR family the ability to effectively perform the same multiply-accumulate operation. This unit is functionally equivalent to a multiplier directly connected to an Arithmetic Logic Unit (ALU). The component that makes a dedicated digital signal processor (DSP) specially suitable for signal processing is the Multiply-Accumulate (MAC) unit.

#HOW TO MULTIPLY BYTES IN CODEVISIONAVR HOW TO#

The second section will show examples of how to efficiently use the multiplier for 16-bit arithmetic. The MULSU and FMULSU instructions are included to improve the speed and code density for multiplication of 16-bit operands. FMULSU, multiplication of a signed fractional number and with an unsigned fractional number. FMULS, multiplication of signed fractional numbers. FMUL, multiplication of unsigned fractional numbers. MULSU, multiplication of a signed integer with an unsigned integer. These are: MUL, multiplication of unsigned integers. To be able to use the multiplier, six new instructions are added to the AVR instruction set. The first section of this document will give some examples of using the multiplier for 8-bit arithmetic. The multiplier can handle both signed and unsigned integer and fractional numbers without speed or code size penalty. This multiplier is capable of multiplying two 8-bit numbers, giving a 16-bit result using only two clock cycles.

#HOW TO MULTIPLY BYTES IN CODEVISIONAVR SERIES#

1 AVR201: Using the AVR Hardware Multiplier Features 8- and 16-bit Implementations Signed and Unsigned Routines Fractional Signed and Unsigned Multiply Executable Example Programs Introduction The megaavr is a series of new devices in the AVR RISC Microcontroller family that includes, among other new enhancements, a hardware multiplier.