12. MIPS Specific Information¶
This chapter discusses the MIPS architecture dependencies in this port of RTEMS. The MIPS family has a wide variety of implementations by a wide range of vendors. Consequently, there are many, many CPU models within it.
IDT docs are online at http://www.idt.com/products/risc/Welcome.html
12.1. CPU Model Dependent Features¶
This section presents the set of features which vary across MIPS
implementations and are of importance to RTEMS. The set of CPU model feature
macros are defined in the file
cpukit/score/cpu/mips/mips.h based upon the
particular CPU model specified on the compilation command line.
12.1.1. Another Optional Feature¶
The macro XXX
12.2. Calling Conventions¶
12.2.1. Processor Background¶
12.2.2. Calling Mechanism¶
12.2.3. Register Usage¶
12.2.4. Parameter Passing¶
12.3. Memory Model¶
12.3.1. Flat Memory Model¶
The MIPS family supports a flat 32-bit address space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4 gigabytes). Each address is represented by a 32-bit value and is byte addressable. The address may be used to reference a single byte, word (2-bytes), or long word (4 bytes). Memory accesses within this address space are performed in big endian fashion by the processors in this family.
Some of the MIPS family members such as the support virtual memory and segmentation. RTEMS does not support virtual memory or segmentation on any of these family members.
12.4. Interrupt Processing¶
Although RTEMS hides many of the processor dependent details of interrupt processing, it is important to understand how the RTEMS interrupt manager is mapped onto the processor’s unique architecture. Discussed in this chapter are the MIPS’s interrupt response and control mechanisms as they pertain to RTEMS.
12.4.1. Vectoring of an Interrupt Handler¶
Upon receipt of an interrupt the XXX family members with separate interrupt stacks automatically perform the following actions:
A nested interrupt is processed similarly by these CPU models with the exception that only a single ISF is placed on the interrupt stack and the current stack need not be switched.
12.4.2. Interrupt Levels¶
12.5. Default Fatal Error Processing¶
The default fatal error handler for this target architecture disables processor interrupts, places the error code in XXX, and executes a``XXX`` instruction to simulate a halt processor instruction.
12.6. Symmetric Multiprocessing¶
SMP is not supported.
12.7. Thread-Local Storage¶
Thread-local storage is not implemented.