Features

PXD10 Product Brief, Rev. 1

Freescale Semiconductor

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Conditional branches not taken execute in a single clock. Branches with successful target prefetching have

an effective execution time of one clock on e200z0h. All other taken branches have an execution time of

two clocks.

Memory load and store operations are provided for byte, halfword, and word (32-bit) data with automatic

zero or sign extension of byte and halfword load data as well as optional byte reversal of data. These

instructions can be pipelined to allow effective single cycle throughput. Load and store multiple word

instructions allow low overhead context save and restore operations. The load/store unit contains a

dedicated effective address adder to allow effective address generation to be optimized. Also, a load-to-use

dependency does not incur any pipeline bubbles for most cases.

The Condition Register unit supports the condition register (CR) and condition register operations defined

by the Power Architecture. The condition register consists of eight 4-bit fields that reflect the results of

certain operations, such as move, integer and floating-point compare, arithmetic, and logical instructions,

and provide a mechanism for testing and branching.

Vectored and autovectored interrupts are supported. Hardware vectored interrupt support is provided to

allow multiple interrupt sources to have unique interrupt handlers invoked with no software overhead.

The CPU includes support for Variable Length Encoding (VLE) instruction enhancements. This allows the

classic PowerPC instruction set to be represented by a modified instruction set made up from a mixture of

16-bit and 32-bit instructions. This results in a significantly smaller code size footprint without affecting

performance noticeably.

The CPU core is enhanced by an additional interrupt source—Non Maskable Interrupt. This interrupt

source is routed directly from package pins, via edge detection logic in the SIU to the CPU, bypassing the

Interrupt Controller completely. Once the edge detection logic is programmed, it can not be disabled,

except by reset. The Non Maskable Interrupt is, as the name suggests, completely un-maskable and when

asserted will always result in the immediate execution of the respective interrupt service routine. The Non

maskable interrupt is not guaranteed to be recoverable.

The CPU core has an additional ‘Wait for Interrupt’ instruction that is used in conjunction with low power

STOP mode. When Low Power Stop mode is selected, this instruction is executed to allow the system

clock to be stopped. An external interrupt source or the system wake-up timer is used to restart the system

clock and allow the CPU to service the interrupt.

Additional features include:

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Load/store unit

— 1-cycle load latency

— Misaligned access support

— No load-to-use pipeline bubbles

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Thirty-two 32-bit general purpose registers (GPRs)

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Separate instruction bus and load/store bus Harvard architecture

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Reservation instructions for implementing read-modify-write constructs

•

Multi-cycle divide (divw) and load multiple (lmw) store multiple (smw) multiple class

instructions, can be interrupted to prevent increases in interrupt latency

•

Extensive system development support through Nexus debug port