MOTOROLA

MC68340 PRODUCT INFORMATION

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CENTRAL PROCESSOR UNIT

The CPU32 is a powerful central processor that supervises system functions, makes decisions, manipulates

data, and directs I/O. A special debugging mode simplifies processor emulation during system debug.

CPU32

The CPU32 is an M68000 family processor specially designed for use as a 32-bit core processor and for

operation over the intermodule bus (IMB). Designers used the MC68020 as a model and included advances

of the later M68000 family processors, resulting in an instruction execution performance of 4 MIPS (VAX-

equivalent) at 25.16 MHz.

The powerful and flexible M68000 architecture is the basis of the CPU32. MC68000 (including the

MC68HC000 and the MC68EC000) and MC68010 user programs will run unmodified on the CPU32. The

programmer can use any of the eight 32-bit data registers for fast manipulation of data and any of the eight

32-bit address registers for indexing data in memory. The CPU32 can operate on data types of single bits,

binary-coded decimal (BCD) digits, and 8, 16, and 32 bits. Peripherals and data in memory can reside

anywhere in the 4-Gbyte linear address space. A supervisor operating mode protects system-level

resources from the more restricted user mode, allowing a true virtual environment to be developed.

Flexible instructions for data movement, arithmetic functions, logical operations, shifts and rotates, bit set

and clear, conditional and unconditional program branches, and overall system control are supported,

including a fast 32

× 32 multiply and 32-bit conditional branches. Instructions, such as table lookup and

interpolate and low power stop, support specific requirements of embedded control applications. Many

addressing modes complement these instructions, including predecrement and postincrement, which allow

simple stack and queue maintenance and scaled indexed for efficient table accesses. Data types and

addressing modes are supported orthogonally by all data operations and with all appropriate addressing

modes. Position-independent code is easily written.

The CPU32 is specially optimized to run with the MC68340's 16-bit data bus. Most instructions execute in

one-half the number of clocks compared to the original MC68000, yielding an overall 1.6 times the

performance of the same-speed MC68000 and measuring 10,045 Dhrystones/sec @ 25.16 MHz

(6,742 Dhrystones/sec @ 16.78 MHz).

Like all M68000 family processors, the CPU32 recognizes interrupts of seven different priority levels and

allows the peripheral to vector the processor to the desired service routine. Internal trap exceptions ensure

proper instruction execution with good addresses and data, allow operating system intervention in special

situations, and permit instruction tracing. Hardware signals can either terminate or rerun bad memory

accesses before instructions process data incorrectly.

The CPU32 offers the programmer full 32-bit data processing performance with complete M68000

compatibility, yet with more compact code than is available with RISC processors. The CPU32 is identical in

all CPU32-based M68300 family products.

BACKGROUND DEBUG MODE

A special operating mode is available in the CPU32 in which normal instruction execution is suspended

while special on-chip microcode performs the functions of a debugger. Commands are received over a

dedicated, high-speed, full-duplex serial interface. Commands allow the manual reading or writing of CPU32

registers, reading or writing of external memory locations, and diversion to user-specified patch code. This

background debug mode permits a much simpler emulation environment while leaving the processor chip in

the target system, running its own debugging operations.