September 24, 1998

EDN's 25th Annual Microprocessor/Microcontroller Directory

Motorola 683xx

For most of the 683xx family, Motorola combined a stripped-down 68020 core with a 16-bit (32-bit for CPU32+) on-chip InterModule Bus, which links the CPU with a device's complex peripherals. The core processor, the CPU32 or CPU32+, is a 68020 CPU for embedded control that lacks memory-management-unit (MMU) or floating-point-unit (FPU) interfaces. The CPU32 and CPU32+ have 16- and 32-bit data buses, respectively. The 32-bit processor has eight general-purpose, 32-bit registers; seven 32-bit address registers; a 32-bit ALU; and separate user and supervisor modes, each with its own stack and separate address and data spaces. The CPU32 is code-compatible with the 68020 but has enhanced addressing modes, including scaled index; address-register indirect with base displacement; and index, program-counter-relative, and 32-bit branch displacements. Postincrement and preincrement/decrement options simplify iterative code. The CPU accesses memory-mapped peripheral- control registers and I/O as addresses in memory.

All 683xxs have a system-integration module featuring system configuration, oscillator and clock dividers, reset and power-down-mode control, chip selects and wait states, parallel I/O with interrupt capability, interrupt configuration/ response, and a software watchdog timer. The external-bus interface has as many as 32 address and 16 data lines (32 for CPU32+) and as many as 12 programmable chip-selection lines. The single-chip Integration Module II allows users to select 32-kHz or 4-MHz clock crystals.

Power management: A low-power-stop (LPSTOP) instruction stops the clock. Devices can run at low frequencies.

Special instructions: The 68020 does not support BCD-pack/unpack, bit-field, compare-and-swap, coprocessor, MMU, module-call/return, and memory-indirect-addressing instructions. New instructions include a table look-up and interpolate and the ability to put the chip into a low-power standby mode.

Development tools: The 683xx leverages the extensive development-tool support from the 68xxx architecture. These tools include assemblers, compilers and debuggers, RTOSs, emulators, and evaluation boards.

Second sources: There are no second sources for the 683xx.

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