From 71993497ea1a9444ec3db6c49354f94d33765c36 Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Fri, 28 Jan 2022 23:21:13 -0500
Subject: [PATCH] $7f (delete) character is a null char. drop it (and $00) when
 checking the read queue.

---
 vt100.modem.S | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/vt100.modem.S b/vt100.modem.S
index 3a2bfc5..a7129ea 100644
--- a/vt100.modem.S
+++ b/vt100.modem.S
@@ -163,6 +163,11 @@ modem_int
 * doesn't access direct page.
 
 * check/clear overrun?
+
+*
+* n.b. - vt100 would drop $00 and $7f characters here - I drop them later.
+*
+
 	mx %11
 
 	phb
@@ -242,6 +247,13 @@ modem_io ent
 	beq :nope
 	lda read_buffer,x
 	inc read_q_tail
+
+* $00 and $7f dropped here.
+	and #$7f
+	beq :read 
+	cmp #$7f
+	beq :read
+
 	plp
 	sec
 	rts