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This section provides an overview of the bit programmer's model of the following families of devices:. The bit MCU and DSC devices have sixteen bit working registers, which are memory-mapped to the first 16 words in data memory. Each of the working registers can act as a data, address, or offset register. The 16th working register W15 operates as a software Stack Pointer for interrupts and calls. Several of the standard working registers have additional functionality for Digital Signal Processor DSP operations as shown:.
For more information on bit DSP features, go to this page. There are four basic classifications:. The bit MCU and DSC instruction set provides a rich suite of instructions that support traditional microcontroller applications and a class of instructions that support math-intensive applications. The majority of the instructions are encoded in a single bit word and execute in a single instruction cycle.
Depending on the device family, the bit MCU and DSC instruction set contains up to 84 instructions, which can be grouped into the functional categories shown in the following table:. Byte operations are indicated by appending a ". B" to the instruction mnemonic, i. The bit MCU and DSC devices support three native Addressing modes for accessing data memory, along with several forms of immediate addressing.
Data accesses may be performed using file register addressing, register direct or indirect addressing, and immediate addressing, allowing a fixed value to be used by the instruction. The data memory address range accessed by each Addressing mode is summarized below:. Instructions use a predetermined address as an operand. This allows the loading of the data from any location in data memory to any working register W0:W15 , and storing the contents of any working register to any location in data memory.
Examples of File Register addressing are shown below:. Register direct addressing is used to access the contents of the 16 working registers W0:W Any working register may be used for any instruction that supports this Addressing mode. Instructions using this Addressing mode use the contents of the specified working register as operands for the operation to be performed. This Addressing mode supports both byte and word access.
Sample instructions which utilize register direct addressing are shown below:. Register Indirect addressing is used to indirectly access any location in data memory by treating the contents of a working register as an Effective Address EA to data memory. Essentially, the contents of the working register become a pointer to the location in data memory which is to be accessed by the instruction. Additionally, the contents of the working register may be modified pre- or post-operation, providing an efficient mechanism for processing data stored sequentially in memory.
The modes of indirect addressing supported are shown below:. In immediate addressing, the instruction encoding contains a predefined constant operand which is used by the instruction. The size of the immediate operand varies with the instruction type. Constants of size 1-bit, 4-bit, 5-bit, 6-bit, 8-bit, bit, bit, and bit are allowed, depending on the instruction. Constants may be signed or unsigned. W15 is the default Stack Pointer SP. This ensures that the SP will point to valid RAM and permits stack availability for exceptions, which may occur before the SP is set by the user software.
The user may reprogram the SP during initialization to any location within the data space. The SP always points to the first available free word Top-of-Stack and fills the software stack, working from lower addresses towards higher addresses. Please visit this page to learn more about EDS addressing. Return to Top.
Development Tools What tools do I need? Add Existing Items From Folders What is USB? How are the Coefficients Calculated? Physical Memory Virtual vs. How does cache work? Programmer's Model This section provides an overview of the bit programmer's model of the following families of devices:. Click here to edit contents of this page. Click here to toggle editing of individual sections of the page if possible.
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Microchip Technology SW006022-1N Data Sheet