Add look ahead interface for working COMPRESSED_ISA #65
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and some other additions to the example: Add simple start.S with minimal trap handler (see https://github.com/cliffordwolf/picorv32/blob/master/firmware/start.S for a bigger version) Add irq interface to attosoc.v for working debug() in picorv32.v Add printf from https://github.com/mpaland/printf Use SITE "L19" for uart output Signed-off-by: Tom Vijlbrief <[email protected]>
ram_ready is always true when using look ahead interface Signed-off-by: Tom Vijlbrief <[email protected]>
Signed-off-by: Tom Vijlbrief <[email protected]>
Signed-off-by: Tom Vijlbrief <[email protected]>
Signed-off-by: Tom Vijlbrief <[email protected]>
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I played a bit with
examples/soc_ecp5_evnand could not get theCOMPRESSED_ISAoption working for non trivial programs (conditional jump destinations got garbled in some situations).
By enabling
debug()inpicorv32.vI could see that a 4-byte instruction at e.g.0x0x0102got bits [31:16] from
0x0x100. The root cause is that the current example does NOT use themem_la_*interface.That is fine when
COMPRESSED_ISAis disabled, but when it is enabled picorv32 sometimes uses theread data already in the next cycle, when it is not yet available. Adding and using the
mem_la_*interface fixes this.I also wondered why
debug()did not showDECODEwhenENABLE_IRQwas enabled, but that was caused byirqbeing set to32'hxbecause it was not used inattosoc.v. I addedirq/eoito the used interface.Some additional changes are (I could create a new PR if you don't like these):
Expand memory to 64K.
Add simple start.S with minimal trap handler
(partially copied from https://github.com/cliffordwolf/picorv32/blob/master/firmware/start.S)
Add printf from https://github.com/mpaland/printf and use it in
firmware.cUse
SITE "L19"for UART output, because I use the ECP5-EVN board in the default factory setting without adding 0-ohm bridges to route UART to the FTDI chip. I use a standard USB-serial adapter to read the output fromL19instead.