From 5d8666b837e1d0386585e351bcc2fa4bfc477946 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 3 Dec 2023 17:57:19 -0500
Subject: [PATCH] Enable the cursor signal; no blink action yet.
---
Components/6845/CRTC6845.hpp | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)
diff --git a/Components/6845/CRTC6845.hpp b/Components/6845/CRTC6845.hpp
index fd7008041..67d065a25 100644
--- a/Components/6845/CRTC6845.hpp
+++ b/Components/6845/CRTC6845.hpp
@@ -112,7 +112,7 @@ template <class T> class CRTC6845 {
void run_for(Cycles cycles) {
auto cyles_remaining = cycles.as_integral();
while(cyles_remaining--) {
- // check for end of visible characters
+ // Check for end of visible characters.
if(character_counter_ == registers_[1]) {
// TODO: consider skew in character_is_visible_. Or maybe defer until perform_bus_cycle?
character_is_visible_ = false;
@@ -122,23 +122,26 @@ template <class T> class CRTC6845 {
perform_bus_cycle_phase1();
bus_state_.refresh_address = (bus_state_.refresh_address + 1) & 0x3fff;
- // check for end-of-line
+ bus_state_.cursor = is_cursor_line_ &&
+ bus_state_.refresh_address == ((registers_[15] | (registers_[14] << 8))&0x3fff);
+
+ // Check for end-of-line.
if(character_counter_ == registers_[0]) {
character_counter_ = 0;
do_end_of_line();
character_is_visible_ = true;
} else {
- // increment counter
+ // Increment counter.
character_counter_++;
}
- // check for start of horizontal sync
+ // Check for start of horizontal sync.
if(character_counter_ == registers_[2]) {
hsync_counter_ = 0;
bus_state_.hsync = true;
}
- // check for end of horizontal sync; note that a sync time of zero will result in an immediate
+ // Check for end of horizontal sync; note that a sync time of zero will result in an immediate
// cancellation of the plan to perform sync if this is an HD6845S or UM6845R; otherwise zero
// will end up counting as 16 as it won't be checked until after overflow.
if(bus_state_.hsync) {
@@ -176,10 +179,14 @@ template <class T> class CRTC6845 {
}
inline void do_end_of_line() {
- // check for end of vertical sync
+ // Check for cursor disable.
+ // TODO: this is handled differently on the EGA, should I ever implement that.
+ is_cursor_line_ &= bus_state_.row_address != (registers_[11] & 0x1f);
+
+ // Check for end of vertical sync.
if(bus_state_.vsync) {
vsync_counter_ = (vsync_counter_ + 1) & 15;
- // on the UM6845R and AMS40226, honour the programmed vertical sync time; on the other CRTCs
+ // On the UM6845R and AMS40226, honour the programmed vertical sync time; on the other CRTCs
// always use a vertical sync count of 16.
switch(personality_) {
case HD6845S:
@@ -199,12 +206,12 @@ template <class T> class CRTC6845 {
do_end_of_frame();
}
} else {
- // advance vertical counter
+ // Advance vertical counter.
if(bus_state_.row_address == registers_[9]) {
bus_state_.row_address = 0;
line_address_ = end_of_line_address_;
- // check for entry into the overflow area
+ // Check for entry into the overflow area.
if(line_counter_ == registers_[4]) {
if(registers_[5]) {
line_counter_ = 0;
@@ -215,13 +222,13 @@ template <class T> class CRTC6845 {
} else {
line_counter_ = (line_counter_ + 1) & 0x7f;
- // check for start of vertical sync
+ // Check for start of vertical sync.
if(line_counter_ == registers_[7]) {
bus_state_.vsync = true;
vsync_counter_ = 0;
}
- // check for end of visible lines
+ // Check for end of visible lines.
if(line_counter_ == registers_[6]) {
line_is_visible_ = false;
}
@@ -234,6 +241,9 @@ template <class T> class CRTC6845 {
bus_state_.refresh_address = line_address_;
character_counter_ = 0;
character_is_visible_ = (registers_[1] != 0);
+
+ // Check for cursor enable.
+ is_cursor_line_ |= bus_state_.row_address == (registers_[10] & 0x1f);
}
inline void do_end_of_frame() {
@@ -266,6 +276,8 @@ template <class T> class CRTC6845 {
int display_skew_mask_ = 1;
unsigned int character_is_visible_shifter_ = 0;
+
+ bool is_cursor_line_ = false;
};
}