From c8eb6e2dd55b4cf1a1e8dd481bfe0b7d66e5ace0 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Thu, 6 Mar 2025 17:20:23 +0100
Subject: [PATCH] Apple II: Document BLTU alternative

---
 doc/apple2.sgml                               | 21 +++++++++++++++++++
 libsrc/apple2/crt0.s                          |  2 +-
 ...c-copy-memcpy.s => integer-basic-compat.s} |  0
 3 files changed, 22 insertions(+), 1 deletion(-)
 rename libsrc/apple2/extra/{lc-copy-memcpy.s => integer-basic-compat.s} (100%)

diff --git a/doc/apple2.sgml b/doc/apple2.sgml
index ffe0e2397..28120577a 100644
--- a/doc/apple2.sgml
+++ b/doc/apple2.sgml
@@ -92,7 +92,28 @@ several useful settings:
 
 </descrip><p>
 
+<descrip>
 
+  <tag/Installing your code in the Language Card/
+  The code in the LC segment will automatically be copied from the end of the
+  binary into the Language Card at startup, even if the segment is empty (a
+  0-byte copy). This allows for tighter code. This code will be copied using the
+  Applesoft BLTU2 function that is available starting with the Apple ][+,
+  but not in the original Apple ][ with an Integer BASIC ROM. This shows as
+  a "RANGE ERROR. STOPPING AT ..." message on startup.
+
+  If you want to target the Integer BASIC original Apple ][, you can link in an
+  alternative implementation of the LC segment loading, at the cost of linking
+  in memcpy (60 bytes):
+
+  Using <tt/apple2-integer-basic-compat.o/ is as simple as placing it on the linker
+  command line like this:
+
+  <tscreen><verb>
+  cl65 -t apple2 myprog.c apple2-integer-basic-compat.o
+  </verb></tscreen>
+
+</descrip>
 
 <sect>Linker configurations<label id="link-configs"><p>
 
diff --git a/libsrc/apple2/crt0.s b/libsrc/apple2/crt0.s
index 4b9a59153..628303687 100644
--- a/libsrc/apple2/crt0.s
+++ b/libsrc/apple2/crt0.s
@@ -122,7 +122,7 @@ basic:  lda     HIMEM
 
         ; Call into Applesoft Block Transfer Up -- which handles zero-
         ; sized blocks well -- to move the content of the LC memory area.
-        jsr     bltu2           ; BLTU2
+        jsr     bltu2
 
         ; Switch in LC bank 2 for R/O and return.
         bit     $C080
diff --git a/libsrc/apple2/extra/lc-copy-memcpy.s b/libsrc/apple2/extra/integer-basic-compat.s
similarity index 100%
rename from libsrc/apple2/extra/lc-copy-memcpy.s
rename to libsrc/apple2/extra/integer-basic-compat.s