RM5231-150-Q PMC-Sierra Inc, RM5231-150-Q Datasheet - Page 15

• Manufacturer Part Number: RM5231-150-Q
• Description: RM5231 Microprocessor with 32-Bit System Bus Data Sheet Released
• Manufacturer: PMC-Sierra Inc

Proprietary and Confidential to PMC-Sierra, Inc and for its Customer’s Internal Use
Document ID: PMC-2002165, Issue 1
3.10 Floating-Point General Register File
3.11 System Control Co-processor (CP0)
3.12 System Control Co-Processor Registers
The floating-point general register file (FGR) is made up of thirty-two 64-bit registers. With the
floating-point load and store double instructions ( LDC1 and SDC1 ), the floating-point unit can
take advantage of the 64-bit wide data cache and issue a floating-point co-processor load or store
doubleword instruction in every cycle.
The floating-point control register space contains two registers; one for determining configuration
and revision information for the coprocessor and one for control and status information. These are
primarily used for diagnostic software, exception handling, state saving and restoring, and control
of rounding modes. To support superscalar operation, the FGR has four read ports and two write
ports, and is fully bypassed to minimize operation latency in the pipeline. Three of the read ports
and one write port are used to support the combined multiply-add instruction while the fourth read
and second write port allows a concurrent floating-point load or store.
The system control co-processor, also called coprocessor 0 or CP0 in the MIPS architecture, is
responsible for the virtual memory sub-system, the exception control system, and the diagnostics
capability of the processor. In the MIPS architecture, the system control co-processor (and thus the
kernel software) is implementation dependent.
The memory management unit controls the virtual memory system page mapping. It consists of an
instruction address translation buffer, ITLB, a data address translation buffer, DTLB, a Joint
instruction and data address translation buffer, JTLB, and co-processor registers used by the virtual
memory mapping sub-system.
The RM5231 incorporates all system control co-processor (CP0) registers on-chip. 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 RM5231 includes registers to
implement a real-time cycle counting facility to aid in cache diagnostic testing and to assist in data
error detection.
Figure 4 shows the CP0 registers.
RM5231™ Microprocessor with 32-bit System Bus Data Sheet
Released
15