diff options
Diffstat (limited to 'cpu/cpu.ml')
| -rw-r--r-- | cpu/cpu.ml | 24 |
1 files changed, 20 insertions, 4 deletions
@@ -95,8 +95,13 @@ let rl, rh, i, ex, exf, pc = let ra = mux read_ihi ra (nadder_nocarry 16 pc (one 16)) in let ihi = mux read_ihi (zeroes 8) ram_read in - let exec = ignore (save_next_read_ihi read_ilow) read_ihi in - let i = ilow ++ ihi in + let read_ilow = save_next_read_ihi read_ilow in + (* When execution has just been read, exec is true, and exec is false the rest of the time *) + let exec = read_ihi in + (* Keep same instruction in register until new instruction is read *) + let si, save_i = loop 16 in + let i = mux exec (reg 16 si) (ilow ++ ihi) in + let i = save_i i in (* Execute instruction if exec is set *) let next_pc = nadder_nocarry 16 pc (two 16) in @@ -127,9 +132,20 @@ let rl, rh, i, ex, exf, pc = let next_pc = mux instr_j next_pc (nadder_nocarry 16 pc (sign_extend 11 16 i_jd)) in (* instruction : jal *) let instr_jal = exec ^& eq_c 5 i_i 0b01001 in - let wr = mux instr_jal wr (const "011") in - let rwd = mux instr_jal rwd next_pc in let next_pc = mux instr_jal next_pc (nadder_nocarry 16 pc (sign_extend 11 16 i_jd)) in + let instr_jalxx = instr_jal in + (* instruction : jr/jalr/jer/jner/jltr/jler/jltru/ljeru *) + let instr_jxxr = exec ^& eq_c 4 (i_i % (1, 4)) 0b0101 in + let f0 = i_i ** 0 in + let instr_jr = (not f0) ^& (eq_c 2 i_f 0) in + let instr_jalr = (not f0) ^& (eq_c 2 i_f 1) in + let instr_jalxx = instr_jalxx ^| (instr_jxxr ^& instr_jalr) in + let cond_jxxr = instr_jxxr ^& (alu_comparer 16 f0 i_f v_ra v_rb ^| instr_jr ^| instr_jalr) in + let next_pc = mux cond_jxxr next_pc v_r in + + (* prologue for jal/jalr *) + let wr = mux instr_jalxx wr (const "011") in + let rwd = mux instr_jalxx rwd next_pc in save_cpu_regs wr rwd ^. save_ram_read (cpu_ram ra we wa d) ^. |