Archipelago » qemu

LatticeMico32 target

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General

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All opcodes including the JUART CSRs are supported.

JTAG UART

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JTAG UART is routed to a serial console device. For the current boards it

is the second one. Ie to enable it in the qemu virtual console window use

the following command line parameters:

  -serial vc -serial vc

This will make serial0 (the lm32_uart) and serial1 (the JTAG UART)

available as virtual consoles.

Programmatically terminate the emulator

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Originally neither the LatticeMico32 nor its peripherals support a

mechanism to shut down the machine. Emulation aware programs can write to a

to a special register within the system control block to shut down the

virtual machine.  For more details see hw/lm32_sys.c. The lm32-evr is the

first BSP which instantiate this model. A (32 bit) write to 0xfff0000

causes a vm shutdown.

Special instructions

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The translation recognizes one special instruction to halt the cpu:

  and r0, r0, r0

On real hardware this instruction is a nop. It is not used by GCC and

should (hopefully) not be used within hand-crafted assembly.

Insert this instruction in your idle loop to reduce the cpu load on the

host.

Ignoring the MSB of the address bus

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Some SoC ignores the MSB on the address bus. Thus creating a shadow memory

area. As a general rule, 0x00000000-0x7fffffff is cached, whereas

0x80000000-0xffffffff is not cached and used to access IO devices. This

behaviour can be enabled with:

  cpu_lm32_set_phys_msb_ignore(env, 1);