A new breed of assembler is now ready in VHDL. Lionel makes his own in bison+flex, which might lag somewhat, but at least there is a functional command-line tool that eats .Y8 files and generates anotated .HYX dumps, along with optional dumps of the symbol table.

Here is one of the example code samples that pass easily:

; ygrec8/y8/asm.y8/gPEAC.y8 ; created by sam. 11 nov. 2023 19:24:01 CET whygee@f-cpu.org ; version sam. 16 déc. 2023 21:34:37 CET ; ; gPEAC perfect moduli < 256/2 (no overflow of byte): ; 2 6 10 26 30 38 50 66 86 114 126 ; orbit length is mod^2 + mod .EQU MOD 10 ; Modulus .EQU ITERATIONS (MOD * (MOD+1)) .ORG 0 ; default start value SET MOD A1; mod (110 iterations) SET ITERATIONS A2 ; loop counter SET 1 R1 ; X SET 0 R2 ; Y SET 0 R3 ; T ADD R2 R2 ; 0+0=0 : clear the Carry flag reloop: ; first step PF R2 IFC ; copy carry flag to carry in ADD R1 R2 SET A1 R3 SUB R2 R3 SET R3 R2 IFC ; modulo ; second step PF R1 IFC ADD R2 R1 ADD -2 A2 OVL -1 IFS ; exit when loop counter expired SET A1 R3 SUB R1 R3 SET R3 R1 IFC ; modulo SET reloop PC

This is the result:

$ ./vasmy8 "-gfinput=../../asm.y8/gPEAC.y8" "-gdump_symbols=1" :00 ; .ORG 0 ; default start value 5188 ;l14: SET MOD A1; mod (110 iterations) 738B ;l15: SET ITERATIONS A2 ; loop counter 0C86 ;l16: SET 1 R1 ; X 0586 ;l17: SET 0 R2 ; Y 0686 ;l18: SET 0 R3 ; T 2D72 ;l19: ADD R2 R2 ; 0+0=0 : clear the Carry flag 85E2 ;l24: PF R2 IFC ; copy carry flag to carry in 2572 ;l25: ADD R1 R2 0E82 ;l27: SET A1 R3 2E62 ;l28: SUB R2 R3 B582 ;l29: SET R3 R2 IFC ; modulo 84E2 ;l32: PF R1 IFC 2C72 ;l33: ADD R2 R1 7376 ;l35: ADD -2 A2 7F97 ;l36: OVL -1 IFS ; exit when loop counter expired 0E82 ;l38: SET A1 R3 2662 ;l39: SUB R1 R3 B482 ;l40: SET R3 R1 IFC ; modulo 3786 ;l42: SET reloop PC ; SYMBOL TABLE DUMP: ; 'MOD' : user_symbol = 10 (x3) ; 'RELOOP' : address_symbol = 6 (x1) ; 'ITERATIONS' : user_symbol = 110 (x1) ; 'VASMY8_VERSION' : user_symbol = 20231212 (x0)

This is a 1.5 pass assembler: Lines where a symbol is undefined get stored for later and are re-assembled at the end. This creates a .HYX where a sequence of .ORG in reverse order are dumped at the end, which stretches a bit the format's convention but it's not an issue if the file is fed into a tool that will reorder the values (such as the upcoming simulator).

With such a tool, a major milestone is reached: it is now possible to write and assemble larger chunks of code and even whole programs, not just small examples. I'm thinking about the Snake program. This allows a better evaluation of the balance of the instruction set, and eventually adapt it.

The snapshots are as usual on gitlab and this one is also mirrored here at YGREC8_20231214.tbz

The doc must be extended and completed but I'm almost ready for the next milestone: the simulator. Which raises a lot of new questions about its structure and organisation, in particular the interfaces.

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