Apple-1-HW
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Apple1_MiST
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more accurate cursor blinking

This commit is contained in:
nino-porcino 2022-01-15 10:56:21 +01:00
parent cb7aeba5a9
commit 22f36f9187
1 changed files with 19 additions and 13 deletions
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32
rtl/display.v
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@ -156,20 +156,24 @@ module display (
end
//////////////////////////////////////////////////////////////////////////
// Cursor blink
// Cursor blinking.
// On the real Apple-I it's made via a 555 configured to trigger 1.92 Hz
reg blink;
reg [22:0] blink_div;
localparam blink_max = 7457385; // 14318180/2/(1.92/2)
localparam blink_thr = blink_max * 3/4; // ~3/4 duty cycle
localparam blink_rewind = blink_thr - (455 * 262); // sets blinking 1 frame before cursor turns on
reg [31:0] blink_cnt;
wire cursor_on = blink_cnt > blink_thr;
always @(posedge sys_clock or posedge reset)
begin
if (reset)
blink_div <= 0;
else
if(pixel_clken) begin
blink_div <= blink_div + 1;
if (blink_div == 23'd0)
blink <= ~blink;
begin
if (reset)
blink_cnt <= 0;
else
if(pixel_clken) begin
if(cpu_clken & w_en & ready) blink_cnt <= blink_rewind; // when a char is received, blinking is turned off briefly
else if(blink_cnt > blink_max) blink_cnt <= 0;
else blink_cnt <= blink_cnt + 1;
end
end
@ -179,8 +183,10 @@ module display (
// vram to font rom to display pipeline assignments
assign cursor = {v_cursor, h_cursor};
assign vram_r_addr = {vram_v_addr, vram_h_addr};
wire [5:0] cursor_character = cursor_on ? 6'd0 : 6'd32;
assign font_char = (vram_r_addr != cursor) ? vram_dout : (blink) ? 6'd0 : 6'd32;
assign font_char = (vram_r_addr != cursor) ? vram_dout : cursor_character;
assign font_pixel = h_dot;
assign font_line = v_dot * 2 + 4;