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add GOSUB

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This commit is contained in:
Raphael Jacquot 2019-02-08 23:59:36 +01:00
parent 5a834d9006
commit bb298832ff
2 changed files with 38 additions and 2 deletions
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6
decstates.v
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@ -17,8 +17,9 @@
`define DEC_LC_LEN 21 // 3n...
`define DEC_LC 22 // 3n[x]
`define DEC_GOTO 30 // 6
`define DEC_GOTO_LOOP 31 // 6[x]
`define DEC_GOTO_EXEC 32 // 6xxx -> exec
`define DEC_GOTO_LOOP 31 // 6[x] -> exec
`define DEC_GOSUB 32 // 7
`define DEC_GOSUB_LOOP 33 // 7[x] -> exec
`define DEC_8X 40 // 8X
`define DEC_80X 41 // 80X
`define DEC_CONFIG 42 // 805
@ -37,5 +38,6 @@
`define DEC_AaX_EXEC 71 // Aax
`define DEC_AbX_EXEC 72 // Abx
`define DEC_BX 80 // Bx
`define DEC_DX 100 // Dx
`endif

34
opcodes/7xxx_GOSUB.v Normal file
View file

@ -0,0 +1,34 @@
/******************************************************************************
* 6xxx GOSUB xxx
*
*
*/
`include "decstates.v"
`include "bus_commands.v"
`DEC_GOSUB: begin
//$display("DEC_GOTO : nibble %h", nibble);
jump_offset <= 0;
t_cnt <= 2;
t_ctr <= 1;
jump_offset[3:0] <= nibble;
rstk_ptr <= rstk_ptr + 1;
decstate <= `DEC_GOSUB_LOOP;
end
`DEC_GOSUB_LOOP: begin
$display("PC %h | t_cnt %d | t_ctr %d | jump_offset %h", PC, t_cnt, t_ctr, jump_offset);
jump_offset[t_ctr*4+:4] <= nibble;
if (t_ctr == t_cnt) begin
new_PC <= PC + 1 + {8'h00, nibble, jump_offset[7:0]};
next_cycle <= `BUSCMD_LOAD_PC;
decstate <= `DEC_START;
RSTK[rstk_ptr] <= PC + 1;
`ifdef SIM
$display("%5h GOSUB\t%3h\t=> %05h",
inst_start_PC,
{nibble, jump_offset[7:0]},
PC + 1 + {8'h00, nibble, jump_offset[7:0]});
`endif
end else t_ctr <= t_ctr + 1;
end