GR740-UM-DS, Nov 2017, Version 1.7
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GR740
5.7
Software portability
5.7.1
Instruction set architecture
The LEON4 processor used in this design implements the SPARC V8 instruction set architecture.
This means that any compiler that produces valid SPARC V8 executables can be used. Full instruction
set compatibility is kept with LEON2FT and LEON3FT applications. The LEON4 processor imple-
ments the SPARC V9 compare and swap (CAS) instruction. This instruction is not available on
LEON2FT and is optional for LEON3FT implementations. Programs that utilize this instruction may
therefore not be backward compatible with legacy systems. See also information about the memory
map in section 5.7.4 below.
5.7.2
Peripherals
All peripherals in the design are IP cores from Cobham Gaisler’s GRLIB IP library. Standard GRLIB
software drivers can be used.
For software driver development, this document describes the capabilities offered by the GR740 sys-
tem. In order to write a generic driver for a GRLIB IP core, that can be used on all systems based on
GRLIB, please also refer to the generic IP core documentation. Note, however, that the generic docu-
mentation may describe functionality not present in this implementation and that this datasheet super-
sedes any IP core documentation.
5.7.3
Plug and play
Standard GRLIB AMBA plug&play layout is used (see sections 37 and 38). The same software rou-
tines used for typical LEON/GRLIB systems can be used.
5.7.4
Memory map
Many LEON2FT and LEON3FT systems use a memory map with ROM mapped at 0x0 and RAM
mapped at 0x40000000. This design has RAM mapped at 0x0 and ROM mapped at 0xC0000000.
This does in general not affect applications running on an operating system but it has implications for
software running on bare-metal. Please refer to operating system documentation to see if and how
special consideration can be taken for systems with RAM at 0x0 and ROM at 0xC0000000.
Differences in memory map may also mean that prebuilt system software images may not be portable
between systems, and need to be rebuilt, even if software makes use of plug’n’play to discover
peripheral register addresses.
5.8
Level-2 cache
The Level-2 (L2) cache controller is disabled after system reset. From a performance perspective it is
recommended that the L2 cache is enabled as early in the boot process as possible. The L2 cache con-
tents must be invalidated when the cache is enabled, see section 9 for details.