September 24, 1998

EDN's 25th Annual Microprocessor/Microcontroller Directory

National Semiconductor COP8
	View block diagram

The COP8's accumulator-based architecture includes six to eight control and data registers, one of which is an 8-bit program-status register. The CPU also includes two 8-bit address registers, a 16-bit stack pointer, and a 15-bit program counter, which the CPU can access as upper and lower 8-bit registers.

The COP8 executes an add, shift, or load in one internal clock (1-µsec period). The compact and relatively simple instruction set executes 77% of the operations in one clock and takes only 1 byte. One reason for the compact instructions is that the architecture, except for the accumulator, is memory-mapped. Also, National based the COP8 on a modified Harvard architecture. COP8 chips can run with external memory for debugging and prototyping code. An 8-bit port serially reads from and writes to external memory and provides emulation control.

Power management: You can slow the COP8's clocks to minimize power dissipation. Idle mode restricts peripheral operations; halt stops the clock. Both modes maintain RAM and enable an interrupt to wake the CPU. You can program and selectively turn off most special peripherals.

Special instructions: The COP8's bit-manipulation instructions include set, clear, various logic instructions, and bit test and skip to next instruction. Math functions include add, subtract, increment, decrement, decimal correct, and complement. Instructions also swap accumulator nibbles and exchange the accumulator and memory. Other special COP8 instructions include decrement register and skip if zero, return from subroutine and skip, and software-trap interrupt.

Special on-chip peripherals: National divides the COP8 family into several product lines, including the ACC, 888xG, 888FH, and 888EB products. The COP8ACC incorporates a user-programmable 16-bit ADC achieving 410-µsec conversion at 12-bit resolution 51 LSB. The COP888xG family comprises nine compatible devices with a common feature set of three multifunction timers, a full-duplex UART, and two analog comparators. The company based the COP888FH on the COP888xG family. The COP888FH integrates a hardware multiply/divide block. The COP888EB targets communications and includes UART, controller-area-network (CAN), serial-peripheral, and Microwire/Plus interfaces and an 8-bit, eight-channel ADC.

The standard COP8 timer comprises a 16-bit counter with two capture/autoreload registers. You can use the timer for external-event capture and counting, internal timekeeping, and processor-independent PWM signal generation. The COP888CF, COP888GD, and COP888EB contain 8 bit, eight-channel, successive-approximation ADCs. For higher resolution A/D conversion of as much as 16 bits, the COP888EK and COP8ACC have an analog function block with a constant current source and a voltage reference. The COP8ACC has a high-speed capture timer that operates at the oscillator frequency. You can tie the output of the analog comparator in the block to the capture input of a timer for integrating single-slope A/D conversion. The COP888EB and COP888BC support passive CAN 2.0B communication. Most COP8s contain full-duplex USARTs with a flexible internal baud-rate generator that generates the UART clock from the oscillator frequency. The COP8s also support ESD protection as high as 5 kV and reduce EMI by as much as 20 dB.

Development tools: National Semiconductor offers a free assembler/linker/librarian via the company's Web site, www.national.com/cop8. KKD (Denmark) provides a Windows-based IDE and project manager. Aisys (www.aisys-usa.com) provides DriveWay COP8, which lets users specify and configure which peripherals they want to use for an application. DriveWay assembles the shell of the program with the peripheral drivers and interrupt support for either National's assembler or ByteCraft's (www.bytecraft.com) C compiler. MetaLink (www.metalink.de) provides three levels of in-circuit emulation and evaluation with a common windowed user interface. The IceMASTER-400 runs at full speed with source-level debugging and 32 kbytes of available breakpoints. Trace capability is as large as 4000 frames, and software-performance analysis is available.

National offers a low-cost debugging module that also operates at full speed but with fewer available breakpoints, a smaller trace memory, and no software-performance analysis. The debugging module also contains a programmer that programs all available EPROM-based devices. National provides an evaluation-and-programming unit for entry-level evaluation and simple in-system development and debugging as well as programming of EPROM-based COP8 µCs. The company also offers low-cost evaluation boards.

Second sources: There are no second sources for the COP8.

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