From 577b01e80b8082c7046250d7b0d213fd9cdd639d Mon Sep 17 00:00:00 2001
From: Ryan Schmidt <git@ryandesign.com>
Date: Sun, 22 Oct 2023 04:38:52 -0500
Subject: [PATCH 1/5] Fix Apple II/II+/IIe vbl rows read addresses
See #1180
---
Machines/Apple/AppleII/Video.hpp | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/Machines/Apple/AppleII/Video.hpp b/Machines/Apple/AppleII/Video.hpp
index 1e84d2c04..79dad3c2b 100644
--- a/Machines/Apple/AppleII/Video.hpp
+++ b/Machines/Apple/AppleII/Video.hpp
@@ -147,8 +147,13 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
// Apply carry into the row counter.
int mapped_row = row_ + (mapped_column / 65);
- mapped_column %= 65;
mapped_row %= 262;
+ mapped_column %= 65;
+
+ // Vertical blanking rows read eight bytes earlier.
+ if(mapped_row >= 192) {
+ mapped_column -= 8;
+ }
// Apple out-of-bounds row logic.
if(mapped_row >= 256) {
@@ -168,20 +173,20 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
@returns @c true if the display will be within vertical blank at now + @c offset; @c false otherwise.
*/
bool get_is_vertical_blank(Cycles offset) {
- // Map that backwards from the internal pixels-at-start generation to pixels-at-end
- // (so what was column 0 is now column 25).
+ // Determine column at offset.
int mapped_column = column_ + int(offset.as_integral());
// Map that backwards from the internal pixels-at-start generation to pixels-at-end
// (so what was column 0 is now column 25).
mapped_column += 25;
- // Apply carry into the row counter and test it for location.
+ // Apply carry into the row counter.
int mapped_row = row_ + (mapped_column / 65);
+ mapped_row %= 262;
// Per http://www.1000bit.it/support/manuali/apple/technotes/iigs/tn.iigs.040.html
// "on the IIe, the screen is blanked when the bit is low".
- return (mapped_row % 262) < 192;
+ return mapped_row < 192;
}
private:
From c272632b5a255a3073ad87758da178eea266dfc7 Mon Sep 17 00:00:00 2001
From: Ryan Schmidt <git@ryandesign.com>
Date: Mon, 23 Oct 2023 05:18:13 -0500
Subject: [PATCH 2/5] Fix Apple II/II+/IIe hbl row < 64 read addresses
See #1180
---
Machines/Apple/AppleII/Video.hpp | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/Machines/Apple/AppleII/Video.hpp b/Machines/Apple/AppleII/Video.hpp
index 79dad3c2b..0beea0828 100644
--- a/Machines/Apple/AppleII/Video.hpp
+++ b/Machines/Apple/AppleII/Video.hpp
@@ -150,6 +150,9 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
mapped_row %= 262;
mapped_column %= 65;
+ // Remember if we're in a horizontal blanking interval.
+ int hbl = mapped_column < 25;
+
// Vertical blanking rows read eight bytes earlier.
if(mapped_row >= 192) {
mapped_column -= 8;
@@ -162,8 +165,17 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
mapped_row %= 192;
}
- // Calculate the address and return the value.
+ // Calculate the address.
uint16_t read_address = uint16_t(get_row_address(mapped_row) + mapped_column - 25);
+
+ if(hbl) {
+ // Wraparound addressing within 128 byte sections.
+ if(mapped_row < 64) {
+ read_address += 128;
+ }
+ }
+
+ // Read the address and return the value.
uint8_t value, aux_value;
bus_handler_.perform_read(read_address, 1, &value, &aux_value);
return value;
From 98730f1f904d582ecad40a59bfb1dee50f47e973 Mon Sep 17 00:00:00 2001
From: Ryan Schmidt <git@ryandesign.com>
Date: Wed, 25 Oct 2023 00:27:18 -0500
Subject: [PATCH 3/5] Fix Apple II/II+/IIe first hbl byte read addresses
Closes #1180
---
Machines/Apple/AppleII/Video.hpp | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Machines/Apple/AppleII/Video.hpp b/Machines/Apple/AppleII/Video.hpp
index 0beea0828..72245c22e 100644
--- a/Machines/Apple/AppleII/Video.hpp
+++ b/Machines/Apple/AppleII/Video.hpp
@@ -153,6 +153,11 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
// Remember if we're in a horizontal blanking interval.
int hbl = mapped_column < 25;
+ // The first column is read twice.
+ if(mapped_column == 0) {
+ mapped_column = 1;
+ }
+
// Vertical blanking rows read eight bytes earlier.
if(mapped_row >= 192) {
mapped_column -= 8;
From c206c7e2cbcad7e4ebba71e3163428bc4266c3b2 Mon Sep 17 00:00:00 2001
From: Ryan Schmidt <git@ryandesign.com>
Date: Wed, 25 Oct 2023 01:44:48 -0500
Subject: [PATCH 4/5] Fix Apple II/II+ text/lores hbl read addresses
Closes #1181
---
Machines/Apple/AppleII/Video.hpp | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/Machines/Apple/AppleII/Video.hpp b/Machines/Apple/AppleII/Video.hpp
index 72245c22e..c2e947a3a 100644
--- a/Machines/Apple/AppleII/Video.hpp
+++ b/Machines/Apple/AppleII/Video.hpp
@@ -178,6 +178,13 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
if(mapped_row < 64) {
read_address += 128;
}
+
+ // On Apple II and II+ (not IIe or later) in text/lores mode (not hires), horizontal
+ // blanking bytes read from $1000 higher.
+ const GraphicsMode pixel_mode = graphics_mode(mapped_row);
+ if(!is_iie_ && ((pixel_mode == GraphicsMode::Text) || (pixel_mode == GraphicsMode::LowRes))) {
+ read_address += 0x1000;
+ }
}
// Read the address and return the value.
From 18ed36d09010b80d627dc595374f00a58833ee9e Mon Sep 17 00:00:00 2001
From: Ryan Schmidt <git@ryandesign.com>
Date: Tue, 24 Oct 2023 19:50:02 -0500
Subject: [PATCH 5/5] Update get_last_read_value source documentation
---
Machines/Apple/AppleII/Video.hpp | 56 ++++++++++++++++++++++++++++----
1 file changed, 49 insertions(+), 7 deletions(-)
diff --git a/Machines/Apple/AppleII/Video.hpp b/Machines/Apple/AppleII/Video.hpp
index c2e947a3a..1af8620ad 100644
--- a/Machines/Apple/AppleII/Video.hpp
+++ b/Machines/Apple/AppleII/Video.hpp
@@ -129,14 +129,56 @@ template <class BusHandler, bool is_iie> class Video: public VideoBase {
*/
uint8_t get_last_read_value(Cycles offset) {
// Rules of generation:
- // (1) a complete sixty-five-cycle scan line consists of sixty-five consecutive bytes of
- // display buffer memory that starts twenty-five bytes prior to the actual data to be displayed.
- // (2) During VBL the data acts just as if it were starting a whole new frame from the beginning, but
- // it never finishes this pseudo-frame. After getting one third of the way through the frame (to
- // scan line $3F), it suddenly repeats the previous six scan lines ($3A through $3F) before aborting
- // to begin the next true frame.
+
+ // FOR ALL MODELS IN ALL MODES:
//
- // Source: Have an Apple Split by Bob Bishop; http://rich12345.tripod.com/aiivideo/softalk.html
+ // - "Screen memory is divided into 128-byte segments. Each segment is divided into the FIRST 40, the
+ // SECOND 40, the THIRD 40, and eight bytes of no man's memory (UNUSED 8)." (5-8*)
+ //
+ // - "The VBL base addresses are equal to the FIRST 40 base addresses minus eight bytes using 128-byte
+ // wraparound subtraction. Example: $400 minus $8 gives $478; not $3F8." (5-11*)
+ //
+ // - "The memory locations scanned during HBL prior to a displayed line are the 24 bytes just below the
+ // displayed area, using 128-byte wraparound addressing." (5-13*)
+ //
+ // - "The first address of HBL is always addressed twice consecutively" (5-11*)
+ //
+ // - "Memory scanned by lines 256 through 261 is identical to memory scanned by lines 250 through 255,
+ // so those six 64-byte sections are scanned twice" (5-13*)
+
+ // FOR II AND II+ ONLY (NOT IIE OR LATER) IN TEXT/LORES MODE ONLY (NOT HIRES):
+ //
+ // - "HBL scanned memory begins $18 bytes before display scanned memory plus $1000." (5-11*)
+ //
+ // - "Horizontal scanning wraps around at the 128-byte segment boundaries. Example: the address scanned
+ // before address $400 is $47F during VBL. The address scanned before $400 when VBL is false is
+ // $147F." (5-11*)
+ //
+ // - "the memory scanned during HBL is completely separate from the memory scanned during HBL´." (5-11*)
+ //
+ // - "HBL scanned memory is in an area normally taken up by Applesoft programs or Integer BASIC
+ // variables" (5-37*)
+ //
+ // - Figure 5.17 Screen Memory Scanning (5-37*)
+
+ // FOR IIE AND LATER IN ALL MODES AND II AND II+ IN HIRES MODE:
+ //
+ // - "HBL scanned memory begins $18 bytes before display scanned memory." (5-10**)
+ //
+ // - "Horizontal scanning wraps around at the 128-byte segment boundaries. Example: the address scanned
+ // before address $400 is $47F." (5-11**)
+ //
+ // - "during HBL, the memory locations that are scanned are in the displayed memory area." (5-13*)
+ //
+ // - "Programs written for the Apple II may well not perform correctly on the Apple IIe because of
+ // differences in scanning during HBL. In the Apple II, HBL scanned memory was separate from other
+ // display memory in TEXT/LORES scanning. In the Apple IIe, HBL scanned memory overlaps other scanned
+ // memory in TEXT/LORES scanning in similar fashion to HIRES scanning." (5-43**)
+ //
+ // - Figure 5.17 Display Memory Scanning (5-41**)
+
+ // Source: * Understanding the Apple II by Jim Sather
+ // Source: ** Understanding the Apple IIe by Jim Sather
// Determine column at offset.
int mapped_column = column_ + int(offset.as_integral());