Terminal: Add support for reading characters.
[firearm.git] / Terminal.v
index 89b19d5..dd041d0 100644 (file)
@@ -12,6 +12,8 @@ module Terminal(
        /* Terminal pretends to be cp5. */
        reg towrite = 0;
        reg [7:0] data = 0;
+       reg [8:0] indata = 0;   /* High bit is if data is present. */
+       reg didread = 0;
        
        always @(*)
        begin
@@ -19,16 +21,25 @@ module Terminal(
                data = 8'hxx;
                cp_ack = 0;
                cp_busy = 0;
+               cp_read = 0;
+               didread = 0;
                if (cp_req && (cp_rnw == 0) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0000) && (cp_insn[11:8] == 4'h5))
                begin
                        towrite = 1;
                        data = cp_write[7:0];
                        cp_ack = 1;
+               end else if (cp_req && (cp_rnw == 1) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0001) && (cp_insn[11:8] == 4'h5))
+               begin
+                       cp_read = {23'h0, indata[8:0]};
+                       cp_ack = 1;
+                       didread = cp_insn[7:5] == 1;
                end
        end
 `ifdef verilator       
        always @(posedge clk)
                if (towrite)
                        $c("{extern void term_output(unsigned char d); term_output(",data,");}");
+               else if (didread || !indata[8])
+                       indata = $c("({extern unsigned int term_input(); term_input();})");
 `endif
 endmodule
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