Annotation of qemu/target-lm32/README, revision 1.1

1.1     ! root        1: LatticeMico32 target
        !             2: --------------------
        !             3: 
        !             4: General
        !             5: -------
        !             6: All opcodes including the JUART CSRs are supported.
        !             7: 
        !             8: 
        !             9: JTAG UART
        !            10: ---------
        !            11: JTAG UART is routed to a serial console device. For the current boards it
        !            12: is the second one. Ie to enable it in the qemu virtual console window use
        !            13: the following command line parameters:
        !            14:   -serial vc -serial vc
        !            15: This will make serial0 (the lm32_uart) and serial1 (the JTAG UART)
        !            16: available as virtual consoles.
        !            17: 
        !            18: 
        !            19: Programmatically terminate the emulator
        !            20: ----------------------------------------
        !            21: Originally neither the LatticeMico32 nor its peripherals support a
        !            22: mechanism to shut down the machine. Emulation aware programs can write to a
        !            23: to a special register within the system control block to shut down the
        !            24: virtual machine.  For more details see hw/lm32_sys.c. The lm32-evr is the
        !            25: first BSP which instantiate this model. A (32 bit) write to 0xfff0000
        !            26: causes a vm shutdown.
        !            27: 
        !            28: 
        !            29: Special instructions
        !            30: --------------------
        !            31: The translation recognizes one special instruction to halt the cpu:
        !            32:   and r0, r0, r0
        !            33: On real hardware this instruction is a nop. It is not used by GCC and
        !            34: should (hopefully) not be used within hand-crafted assembly.
        !            35: Insert this instruction in your idle loop to reduce the cpu load on the
        !            36: host.
        !            37: 
        !            38: 
        !            39: Ignoring the MSB of the address bus
        !            40: -----------------------------------
        !            41: Some SoC ignores the MSB on the address bus. Thus creating a shadow memory
        !            42: area. As a general rule, 0x00000000-0x7fffffff is cached, whereas
        !            43: 0x80000000-0xffffffff is not cached and used to access IO devices. This
        !            44: behaviour can be enabled with:
        !            45:   cpu_lm32_set_phys_msb_ignore(env, 1);
        !            46: 

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