September 24, 1998

EDN's 25th Annual Microprocessor/Microcontroller Directory

Oki nX 65K
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Oki's 65K series chips combine an 8-bit core with an 8-bit bus. Although these µCs with 83 instructions are code-incompatible with the 8051, a translator package and some handiwork can translate code from one to another. Oki also sells an nX 66K series, an extension of the 65K core with a 16-bit core and an 8-bit bus. The nX 65K has four sets of 16 local registers mapped into data memory. One set acts as the current set for processing; switching to a new set makes for a fast context switch because no registers have to be saved. Four of the 8-bit registers in each set can function as two 16-bit registers for addressing. The 65K core also has two accumulators, a stack pointer, a program-status word (PSW), and a 16-bit program counter.

The 65K series chips have a 64-kbyte address space for instructions and data. Memory-mapped special-function registers control the peripherals. The 65K series lacks specialized data-memory segments that require special addressing or logically overlap other segments. The 65K blocks local memory into 256-byte pages; a field in the PSW enables reference to these pages. Code can address paged memory using 8-bit registers. Main-memory accesses require 16-bit addresses. The 65K distinguishes between local, 8-bit, addressable paged memory and general, 16-bit, addressable memory.

Power management: Halt mode discontinues the CPU function with peripherals still functioning. Stop mode stops the clock and all functions other than interrupt. New devices have a dual clock. Improved throughput, which allows for lower clock frequencies, saves power under normal operation.

Special instructions: The nX 65K's bit-manipulation instructions are set, clear, transfer to carry, jump on bit set, and jump on bit clear. Math functions include add, subtract, increment, decrement, multiply, divide, and decimal adjustment after add or subtract. The CPU also has a parity-check instruction.

Special on-chip peripherals: Every 8-bit nX 65K is available in masked-ROM, ROMless, and one-time-programmable versions. The MSM65355 has a special input module to capture and decode remote-control signals, such as those that TV remote controllers use.

Development tools: A variety of hardware and software tools is available for Oki's nX 65K. A program-development system, the OMFICE in-circuit emulator, works with evaluation models. Software includes a relocatable assembler, a linker, a librarian, a symbolic debugger, an object converter, and an 80C51 translator. In addition to Oki's OMFICE, third-party emulators are available from MetaLink (www.metalink.de) and Yokogawa Digital (www.yokogawa.com). IAR (www.iar.com) offers a C compiler to support the 65K series.

Second sources: There are no second sources for the nX 65K.

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