[qemu.git] / target-lm32 / README

LatticeMico32 target
--------------------

General
-------
All opcodes including the JUART CSRs are supported.


JTAG UART
---------
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
----------------------------------------
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
--------------------
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
-----------------------------------
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);
Commit	Line	Data
45664345 MW	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