Execution Core

  • Execution Core
  • This section provides an overview of the EXECUTION CORE functional block, the primary component of the processor.

    • For details on the instruction set and local hardware devices, see 'Software » ISA Specification'
    • For details on memory bus timing and operation, see 'Design » Bus Specifications'

  • System Memory Bus

    The main system memory bus operates on a 64-bit address with 16-bit data. In addition to the primary address, there is a 2-bit memory 'region' which effectively extends the address to 66 bits; the MBUS_ADDRESS_REGION selects between four endpoints on the memory bus (similar to the X86 I/O M_IO pin and I/O instructions) and can be set by the core through the ADDRES_REGION register.

    Net ports:
    • MBUS_ADDRESS[63:0] - Output from core, primary address bus.
    • MBUS_ADDRESS_REGION[1:0] - Output from core, selects active memory device.
    • MBUS_DATA_D[15:0] - Input to core, primary data bus.
    • MBUS_DATA_Q[15:0] - Output from core, primary data bus.
    • MBUS_WRITE_READ_N - Output from core, controls whether data is being read from or written to memory.
    • MBUS_ADDRESS_VALID - Output from core, flow control indicates that the bus request is valid.
    • MBUS_DATA_VALID - Input to core, flow control indicates that data is ready on the bus.

  • Interrupt Controller

    The interrupt controller encodes an arbitrary number of interrupt lines (the current implementation has five interrupt lines available) into a queue of interrupt identifiers which is presented to the processor core. Interrupts are latched on the rising edge of the corresponding IREQ input

    Net ports:
    • IREQ - Input from interrupt controller, indicating that an active interrupt is waiting.
    • IREQ_IDENT[15:0] - Input from interrupt controller, front of interrupt identifier queue.
    • IREQ_ACK - Output to interrupt controller, dequeues the last active interrupt.

Block Diagrams
  • Program Address Control Address Control

    (In Progress)

  • Datapath Datapath

    (In Progress)

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