MC68306 Motorola, MC68306 Datasheet - Page 69

• Manufacturer Part Number: MC68306
• Description: Integrated EC000 Processor
• Manufacturer: Motorola

SECTION 4
EC000 CORE PROCESSOR
The EC000 core has a 16-bit data bus and 32-bit address bus while the full architecture
provides for 32-bit address and data register operations.
4.1 FEATURES
The following resources are available to the EC000 core:
4.2 PROCESSING STATES
The processor is always in one of three states: normal processing, exception processing,
or halted. It is in the normal processing state when executing instructions, fetching
instructions and operands, and storing instruction results.
Exception processing is the transition from program processing to system, interrupt, and
exception handling. Exception processing includes fetching the exception vector, stacking
operations, and refilling the instruction pipe after an exception. The processor enters
exception processing when an exceptional internal condition arises such as tracing an
instruction, an instruction results in a trap, or executing specific instructions. External
conditions, such as interrupts and access errors, also cause exceptions. Exception
processing ends when the first instruction of the exception handler begins to execute.
The processor halts when it receives an access error or generates an address error while
in the exception processing state. For example, if during exception processing of one
access error another access error occurs, the processor is unable to complete the
transition to normal processing and cannot save the internal state of the machine. The
processor assumes that the system is not operational and halts. Only an external reset
can restart a halted processor. Note that when the processor executes a STOP
instruction, it is in a special type of normal processing state, one without bus cycles. The
processor stops, but it does not halt.
MOTOROLA
• 8 32-Bit Address Registers
• 8 32-Bit Data Registers
• 4-Gbyte Direct Addressing Range
• 56 Powerful Instructions
• Operations on Five Main Data Types
• Memory-Mapped Input/Output (I/O)
• 14 Addressing Modes
MC68306 USER'S MANUAL
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