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ACT-7000SC-266F17T Datasheet(PDF) 6 Page - Aeroflex Circuit Technology |
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ACT-7000SC-266F17T Datasheet(HTML) 6 Page - Aeroflex Circuit Technology |
6 / 25 page Aeroflex Circuit Technology SCD7000SC REV B 7/30/01 Plainview NY (516) 694-6700 6 address translation buffer, or DTLB, a Joint TLB, or JTLB, and coprocessor registers used by the virtual memory mapping sub-system. System Control Coprocessor Registers The ACT 7000SC incorporates all system control coprocessor (CP0) registers internally. These registers provide the path through which the virtual memory system’s page mapping is examined and modified, exceptions are handled, and operating modes are controlled (kernel vs. user mode, interrupts enabled or disabled, cache features). In addition, the ACT 7000SC includes registers to implement a real-time cycle counting facility, to aid in cache and system diagnostics, and to assist in data error detection. To support the non-blocking caches and enhanced interrupt handling capabilities of the ACT 7000SC, both the data and control register spaces of CP0 are supported by the ACT 7000SC. In the data register space, that is the space accessed using the MFC0 and MTC0 instructions, the ACT 7000SC supports the same registers as found in the RM5200, R4000 and R5000 families. In the control space, that is the space accessed by the previously unused CTC0 and CFC0 instructions, the ACT 7000SC supports five new registers. The first three of these new 32-bit registers support the enhanced interrupt handling capabilities and are the Interrupt Control, Interrupt Priority Level Lo (IPLLO), and Interrupt Priority Level Hi (IPLHI) registers. These registers are described further in the section on interrupt handling. The other two registers, Imprecise Error 1 and Imprecise Error 2, have been added to help diagnose bus errors which occur on non-blocking memory references. Figure 4 shows the CP0 registers. Virtual to Physical Address Mapping The ACT 7000SC provides three modes of virtual addressing: • user mode • supervisor mode • kernel mode This mechanism is available to system software to provide a secure environment for user processes. Bits in the CP0 Status register determine which virtual addressing mode is used. In the user mode, the ACT 7000SC provides a single, uniform virtual address space of 256GB (2GB in 32-bit mode). When operating in the kernel mode, four distinct virtual address spaces, totalling 1024GB (4GB in 32-bit mode), are simultaneously available and are differentiated by the high-order bits of the virtual address. The ACT 7000SC processor also supports a supervisor mode in which the virtual address space is 256.5GB (2.5GB in 32-bit mode), divided into three regions based on the high-order bits of the virtual address. Figure 5 shows the address space layout for 32-bit operation. Info 7* Index 0* Random 1* Wired 6* PRid 15* LLAddr 17* TagLo 28* TagHi 29* EPC 14* ECC 26* Status 12* Context 4* Count 9* BadVAddr 8* Compare 11* Cause 13* Watch1 18* Watch2 19* ErrorEPC 30* Config 16* Perf Counter 25* Perf Ctr Cntrl 22* Watch Mask 24* IPLHI 19* IPLLO 18* IntControl 20* Imp Error 1 26* Imp Error 2 27* PageMask 5* EntryHi 10* EntryLo1 3* EntryLo0 2* TLB (entries protected from TLBWR) Used for memory management * Registered number Used for exception processing Control Space Registers Xcontext 20* CacheErr 27* 47 0 Figure 4 – CP0 Registers |
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