Corthay, Francois

NanoBlaze: the expandable processor

Line 312, you have to put "," to correct the syntax error

Syntax error - file nanoProcessor

The assembler converts all conditional RETURN statements (RETURN Z/NZ/C/NC) into unconditional RETURN, requiring the use of a conditional JUMP over the unconditional RETURN.  There is no warning given that this assembler operation is being coded into the program ROM.

This is not a major limitation, but it is a variance from the PicoBlaze instruction set.  When I re-enabled the conditional RETURN statements, I found that the issue is with the VHDL source files.  Regardless of whether the condition statement is true or false, the conditional RETURN always pops an address off the call stack.  In a loop, the effect is to continually pop nonexistent return addresses from the stack.

The bug is that no indication is given to the user that his conditional RETURN has been converted to unconditional RETURN.

No conditional RETURN statements

The perl script assembler fails to distinguish between labels that differ only in that one has a single digit appended.  For example, these two labels are OK:
		"test_val1" and "test_val2"
but these two do not work:
		"test_val" and "test_val1"

It appears to be OK if the additional character is a non-digit character.  For example, these are OK:
		"test_val" and "test_vala"

Assembler issue

Your test code shows single-register STORE/FETCH operations working, but the address is incorrect so the STORE/FETCH access the wrong scratch register.  Since they both error identically, the test passed.

Single-register STORE/FETCH do not work

In the perl script, line 490, the RL opcode expands as "s/RL/shRotL & shRotLdH/", but parameter shRotLdH is not defined.  I changed it to "s/RL/shRotL & shRotLdM/" and re-ran the nanoTest program.  It works.

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NanoBlaze: the expandable processor