From 8fa8d8d1fa1fedaaa3871bce2f7514bf742166ec Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Sat, 8 Jan 2022 22:26:34 -0500
Subject: [PATCH] move modem q variables to the direct page, adjust CDA hexdump
 to show most recent 16*8 bytes.

---
 vt.equ.S      |  8 ++++++++
 vt100.cda.S   | 11 +++++++++--
 vt100.modem.S | 36 ++++++++++++++++++++----------------
 3 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/vt.equ.S b/vt.equ.S
index c8b30ad..2883419 100644
--- a/vt.equ.S
+++ b/vt.equ.S
@@ -84,6 +84,14 @@ saved_x	ds 2
 saved_y	ds 2
 saved_decom ds 2
 
+
+* async read/write pointers.
+*
+read_q_head	ds 2
+read_q_tail	ds 2
+write_q_head	ds 2
+write_q_tail	ds 2
+
 	do *>256
 	err "too big"
 	fin
diff --git a/vt100.cda.S b/vt100.cda.S
index a026d78..a4074c0 100644
--- a/vt100.cda.S
+++ b/vt100.cda.S
@@ -535,13 +535,20 @@ hexdump
 
 	php
 	lda #0
+
+	stz :offset
+
 	sep #$20
 
 	ldx #4*2
 	stx :row
 
-	ldy #0
-	sty :offset
+	lda DPAGE+read_q_tail
+	sec
+	sbc #8*16
+	sta :offset
+
+
 
 :one_row
 
diff --git a/vt100.modem.S b/vt100.modem.S
index 58c9d9e..7daa20b 100644
--- a/vt100.modem.S
+++ b/vt100.modem.S
@@ -6,7 +6,7 @@
 
 	mx %11
 	cas se
-*	use vt.equ
+	use vt.equ
 
 SCCBREG		equ $c038
 SCCAREG		equ $c039
@@ -35,13 +35,15 @@ init_modem ent
 	php
 	sei
 
-	stz q_head
-	stz q_tail
+	stz read_q_head
+	stz read_q_tail
+	stz write_q_head
+	stz write_q_tail
 
 
 * zero out the buffer [for CDA debugger]
 	ldx #0
-]loop	stz buffer,x
+]loop	stz read_buffer,x
 	inx
 	bne ]loop
 
@@ -144,7 +146,7 @@ read_modem_sync ent
 :rts	rts
 
 
-buffer equ $1e00
+read_buffer equ $1e00
 
 modem_vector	ent
 	jml modem_int
@@ -171,9 +173,9 @@ modem_int
 
 :read
 	lda SCCBDATA
-	ldx q_tail
-	sta buffer,x
-	inc q_tail
+	ldx DPAGE+read_q_tail
+	sta read_buffer,x
+	inc DPAGE+read_q_tail
 
 * more?
 	stz SCCBREG
@@ -207,12 +209,12 @@ read_modem_async ent
 
 	php
 	sei
-	ldx q_head
-	cpx q_tail
+	ldx read_q_head
+	cpx read_q_tail
 	beq :nope
 
-	lda buffer,x
-	inc q_head
+	lda read_buffer,x
+	inc read_q_head
 	plp
 	sec
 	rts
@@ -226,13 +228,15 @@ reset_modem_buffer ent
 	mx %11
 	php
 	sei
-	stz q_head
-	stz q_tail
+
+	stz read_q_head
+	stz read_q_tail
+	stz write_q_head
+	stz write_q_tail
+
 	plp
 	rts
 
-q_head	ds 2
-q_tail	ds 2
 *buffer	ds 256
 
 	sav vt100.modem.L