mirror of
https://github.com/sxpert/hp-saturn
synced 2025-01-19 10:26:58 +01:00
34 lines
956 B
Verilog
34 lines
956 B
Verilog
/******************************************************************************
|
|
* 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] <= nb_in;
|
|
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] <= nb_in;
|
|
if (t_ctr == t_cnt) begin
|
|
new_PC <= PC + 1 + {8'h00, nb_in, 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,
|
|
{nb_in, jump_offset[7:0]},
|
|
PC + 1 + {8'h00, nb_in, jump_offset[7:0]});
|
|
`endif
|
|
end else t_ctr <= t_ctr + 1;
|
|
end
|