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COP8SGR740D6 Datasheet(PDF) 3 Page - National Semiconductor (TI) |
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COP8SGR740D6 Datasheet(HTML) 3 Page - National Semiconductor (TI) |
3 / 62 page ![]() 1.0 Device Description 1.1 ARCHITECTURE The COP8 family is based on a modified Harvard architec- ture, which allows data tables to be accessed directly from program memory. This is very important with modern microcontroller-based applications, since program memory is usually ROM or EPROM, while data memory is usually RAM. Consequently data tables need to be contained in non-volatile memory, so they are not lost when the micro- controller is powered down. In a modified Harvard architec- ture, instruction fetch and memory data transfers can be overlapped with a two stage pipeline, which allows the next instruction to be fetched from program memory while the current instruction is being executed using data memory. This is not possible with a Von Neumann single-address bus architecture. The COP8 family supports a software stack scheme that allows the user to incorporate many subroutine calls. This capability is important when using High Level Languages. With a hardware stack, the user is limited to a small fixed number of stack levels. 1.2 INSTRUCTION SET In today’s 8-bit microcontroller application arena cost/ performance, flexibility and time to market are several of the key issues that system designers face in attempting to build well-engineered products that compete in the marketplace. Many of these issues can be addressed through the manner in which a microcontroller’s instruction set handles process- ing tasks. And that’s why COP8 family offers a unique and code-efficient instruction set — one that provides the flexibil- ity, functionality, reduced costs and faster time to market that today’s microcontroller based products require. Code efficiency is important because it enables designers to pack more on-chip functionality into less program memory space. Selecting a microcontroller with less program memory size translates into lower system costs, and the added security of knowing that more code can be packed into the available program memory space. 1.2.1 Key Instruction Set Features The COP8 family incorporates a unique combination of in- struction set features, which provide designers with optimum code efficiency and program memory utilization. Single Byte/Single Cycle Code Execution The efficiency is due to the fact that the majority of instruc- tions are of the single byte variety, resulting in minimum program space. Because compact code does not occupy a substantial amount of program memory space, designers can integrate additional features and functionality into the microcontroller program memory space. Also, the majority instructions executed by the device are single cycle, result- ing in minimum program execution time. In fact, 77% of the instructions are single byte single cycle, providing greater code and I/O efficiency, and faster code execution. 1.2.2 Many Single-Byte, Multifunction Instructions The COP8 instruction set utilizes many single-byte, multi- function instructions. This enables a single instruction to accomplish multiple functions, such as DRSZ, DCOR, JID, LD (Load) and X (Exchange) instructions with post- incrementing and post-decrementing, to name just a few examples. In many cases, the instruction set can simulta- neously execute as many as three functions with the same single-byte instruction. JID: (Jump Indirect); Single byte instruction; decodes exter- nal events and jumps to corresponding service routines (analogous to “DO CASE” statements in higher level lan- guages). LAID: (Load Accumulator-Indirect); Single byte look up table instruction provides efficient data path from the program memory to the CPU. This instruction can be used for table lookup and to read the entire program memory for checksum calculations. RETSK: (Return Skip); Single byte instruction allows return from subroutine and skips next instruction. Decision to branch can be made in the subroutine itself, saving code. AUTOINC/DEC: (Auto-Increment/Auto-Decrement); These instructions use the two memory pointers B and X to effi- ciently process a block of data (analogous to “FOR NEXT” in higher level languages). 1.2.3 Bit-Level Control Bit-level control over many of the microcontroller’s I/O ports provides a flexible means to ease layout concerns and save board space. All members of the COP8 family provide the ability to set, reset and test any individual bit in the data memory address space, including memory-mapped I/O ports and associated registers. 1.2.4 Register Set Three memory-mapped pointers handle register indirect ad- dressing and software stack pointer functions. The memory data pointers allow the option of post-incrementing or post- decrementing with the data movement instructions (LOAD/ EXCHANGE). And 15 memory-maped registers allow de- signers to optimize the precise implementation of certain specific instructions. 1.3 EMI REDUCTION The COP8SGx5 family of devices incorporates circuitry that guards against electromagnetic interference — an increasing problem in today’s microcontroller board designs. National’s patented EMI reduction technology offers low EMI clock circuitry, gradual turn-on output drivers (GTOs) and internal I CC smoothing filters, to help circumvent many of the EMI issues influencing embedded control designs. National has achieved 15 dB–20 dB reduction in EMI transmissions when designs have incorporated its patented EMI reducing cir- cuitry. 1.4 PACKAGING/PIN EFFICIENCY Real estate and board configuration considerations demand maximum space and pin efficiency, particularly given today’s high integration and small product form factors. Microcon- troller users try to avoid using large packages to get the I/O needed. Large packages take valuable board space and increases device cost, two trade-offs that microcontroller designs can ill afford. The COP8 family offers a wide range of packages and do not waste pins: up to 90.9% (or 40 pins in the 44-pin package) are devoted to useful I/O. www.national.com 3 |
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