
1-6
G2 PowerPC Core Reference Manual
For More Information On This Product,
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MOTOROLA
Overview
exception of strings and multiples, generate exceptions under the same
circumstances as big-endian accesses.
— The G2_LE core supports true little-endian mode to minimize the impact on
software porting from true little-endian systems.
— A new input interrupt signal, core_cint, is provided to trigger the critical interrupt
exception on the G2_LE core.
— The G2 core does not have misalignment support for
eciwx
and
ecowx
graphics
instructions. These instructions cause an alignment exception if the access is not
on a word boundary.
Bus clock—New bus multipliers are selected by the encodings of core_pll_cfg[0:4].
Instruction timing
— The integer divide instructions,
divwu
[
o
][
.
]
and
divw
[
o
][
.
], execute in 20 clock
cycles; execution of these instructions in the original PID6 MPC603e device
takes 37 clock cycles.
— Support for single-cycle store
— An adder/comparator added to system register unit that allows dispatch and
execution of multiple integer add and compare instructions on each cycle.
Enhanced debug features
— Addition of three breakpoint registers—IABR2, DABR, and DABR2
— Two new breakpoint control registers—DBCR and IBCR
— Inclusion of four breakpoint signals—core_iabr, core_iabr2, core_dabr, and
core_dabr2
Figure 1-1 provides a block diagram of the G2 core that shows how the execution
units—IU, FPU, BPU, LSU, and SRU—operate independently and in parallel. Note that
this is a conceptual diagram and does not attempt to show how these features are physically
implemented on the chip.
The G2 core provides address translation and protection facilities, including an ITLB,
DTLB, and instruction and data BAT arrays. Instruction fetching and issuing is handled in
the instruction unit. Translation of addresses for cache or external memory accesses are
handled by the MMUs. Both units are discussed in more detail in Section 1.1.3, “Instruction
Unit,” and Section 1.1.6.1, “Memory Management Units (MMUs).”
1.1.2
G2_LE-Specific Features
The following sections describe some of the additional features of the G2_LE core. For a
table summary of the differences between the G2 core and the G2_LE cores, see
Section 1.4, “Differences Between the MPC603e and the G2 and G2_LE Cores.”
F
Freescale Semiconductor, Inc.
n
.