root / target-lm32 / README @ 992aeb8e
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LatticeMico32 target |
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General |
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All opcodes including the JUART CSRs are supported. |
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JTAG UART |
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JTAG UART is routed to a serial console device. For the current boards it |
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is the second one. Ie to enable it in the qemu virtual console window use |
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the following command line parameters: |
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-serial vc -serial vc |
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This will make serial0 (the lm32_uart) and serial1 (the JTAG UART) |
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available as virtual consoles. |
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Programmatically terminate the emulator |
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Originally neither the LatticeMico32 nor its peripherals support a |
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mechanism to shut down the machine. Emulation aware programs can write to a |
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to a special register within the system control block to shut down the |
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virtual machine. For more details see hw/lm32_sys.c. The lm32-evr is the |
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first BSP which instantiate this model. A (32 bit) write to 0xfff0000 |
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causes a vm shutdown. |
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Special instructions |
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The translation recognizes one special instruction to halt the cpu: |
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and r0, r0, r0 |
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On real hardware this instruction is a nop. It is not used by GCC and |
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should (hopefully) not be used within hand-crafted assembly. |
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Insert this instruction in your idle loop to reduce the cpu load on the |
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host. |
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Ignoring the MSB of the address bus |
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----------------------------------- |
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Some SoC ignores the MSB on the address bus. Thus creating a shadow memory |
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area. As a general rule, 0x00000000-0x7fffffff is cached, whereas |
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0x80000000-0xffffffff is not cached and used to access IO devices. This |
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behaviour can be enabled with: |
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cpu_lm32_set_phys_msb_ignore(env, 1); |
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