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MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
1-14
Freescale Semiconductor
Most arithmetic and logical operations are executed in a single cycle with the exception of multiply, which
is implemented with a pipelined hardware array, and the divide instructions. The CLZ unit operates in a
single clock cycle.
The instruction unit contains a program counter (PC) incrementer and a dedicated branch address adder to
minimize delays during change of flow operations. Sequential prefetching is performed to ensure a supply
of instructions into the execution pipeline. Branch target prefetching is performed to accelerate taken
branches. Prefetched instructions are placed into an instruction buffer capable of holding six sequential
instructions and two branch target instructions.
Branch target addresses are calculated in parallel with branch instruction decode, resulting in execution
time of three clocks. Conditional branches which are not taken execute in a single clock. Branches with
successful lookahead and target prefetching have an effective execution time of one clock.
Memory load and store operations are provided for byte, halfword, word (32-bit), and doubleword data
with automatic zero or sign extension of byte and halfword load 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.
The condition register unit supports the condition register (CR) and condition register operations defined
by the Power Architecture technology. 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 auto-vectored interrupts are supported by the CPU. Vectored interrupt support is provided to
allow multiple interrupt sources to have unique interrupt handlers invoked with no software overhead.
The signal processing extension (SPE) APU supports vector instructions (SIMD) operating on 16- and
32-bit fixed-point data types, as well as 32-bit IEEE
-754 single-precision floating-point formats, and
supports single-precision floating-point operations in a pipelined fashion. The 64-bit general-purpose
register file is used for source and destination operands, and there is a unified storage model for
single-precision floating-point data types of 32-bits and the normal integer type. Low latency fixed-point
and floating-point add, subtract, multiply, divide, compare, and conversion operations are provided, and
most operations can be pipelined.
1.5.2
System Bus Crossbar Switch
The system bus’s XBAR multi-port crossbar switch supports simultaneous connections between
three(MPC5554) or four (MPC5553) master ports and five slave ports. The crossbar supports a 32-bit
address bus width and a 64-bit data bus width at all master and slave ports.
The crossbar allows for concurrent transactions to occur from any master port to any slave port. It is
possible for all master ports and slave ports to be in use at the same time as a result of independent master
requests. If a slave port is simultaneously requested by more than one master port, arbitration logic will
select the higher priority master and grant it ownership of the slave port. All other masters requesting that
slave port will be stalled until the higher priority master completes its transactions. By default, requesting
masters will be treated with equal priority and will be granted access to a slave port in round-robin fashion,
based upon the ID of the last master to be granted access.
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