From ba05ac5d74e2e4108dbbb66c8cbde6547b9ea182 Mon Sep 17 00:00:00 2001
From: steve <jscrane@gmail.com>
Date: Tue, 26 Sep 2023 11:35:47 +0100
Subject: [PATCH] move Apple1-dependent bits onto io class

---
 io.cpp  | 23 +++++++++++++++++++++--
 io.h    |  2 ++
 pia.cpp |  3 +++
 pia.h   | 39 +++++++++------------------------------
 4 files changed, 35 insertions(+), 32 deletions(-)

diff --git a/io.cpp b/io.cpp
index 4b5ac88..3ad6247 100644
--- a/io.cpp
+++ b/io.cpp
@@ -78,13 +78,14 @@ static const uint8_t shiftmap[] PROGMEM = {
 };
 
 void io::down(uint8_t scan) {
-	set_porta(0);
+	PIA::write_porta(0);
 	if (isshift(scan))
 		_shift = true;
 }
 
 void io::enter(uint8_t key) {
-	set_porta(key + 0x80);
+	PIA::write_porta(key + 0x80);
+	PIA::write_porta_cr(0xa7);
 }
 
 void io::up(uint8_t scan) {
@@ -145,8 +146,17 @@ void io::write_portb(uint8_t b) {
 	PIA::write_portb(b);
 }
 
+void io::write_portb_cr(uint8_t b) {
+	if (PIA::read_portb_cr() < 0x80)
+		PIA::write_portb_cr(b);
+}
+
 uint8_t io::read_porta_cr() {
 	uint8_t b = PIA::read_porta_cr();
+	if (b & 0x80) {
+		PIA::write_porta_cr(0);
+		b = 0xa7;
+	}
 	if (b != 0xa7)
 		return b;
 
@@ -159,6 +169,15 @@ uint8_t io::read_porta_cr() {
 	return b;
 }
 
+void io::write_porta_cr(uint8_t b) {
+	uint8_t cr = PIA::read_porta_cr();
+	if (!(cr & 0x80) && b >= 0x80)
+		cr |= 0x80;
+	else
+		cr = b;
+	PIA::write_porta_cr(cr);
+}
+
 void io::checkpoint(Stream &s) {
 	PIA::checkpoint(s);
 	s.write(r);
diff --git a/io.h b/io.h
index e11a40e..81743bb 100644
--- a/io.h
+++ b/io.h
@@ -16,7 +16,9 @@ public:
 	virtual void restore(Stream &);
 
 	virtual void write_portb(uint8_t);
+	virtual void write_portb_cr(uint8_t);
 	virtual uint8_t read_porta_cr();
+	virtual void write_porta_cr(uint8_t);
 
 	void load();
 	filer &files;
diff --git a/pia.cpp b/pia.cpp
index 82fa487..62217ad 100644
--- a/pia.cpp
+++ b/pia.cpp
@@ -2,6 +2,9 @@
 #include <memory.h>
 #include "pia.h"
 
+// see: https://github.com/mamedev/mame/blob/master/src/devices/machine/6821pia.cpp
+// and: https://github.com/mamedev/mame/blob/master/src/devices/machine/6821pia.h
+
 void PIA::write(Memory::address a, uint8_t b) {
 #if defined(DEBUGGING)
 	Serial.print(millis());
diff --git a/pia.h b/pia.h
index 3e0906f..e07c275 100644
--- a/pia.h
+++ b/pia.h
@@ -4,8 +4,8 @@
 // https://en.wikipedia.org/wiki/Peripheral_Interface_Adapter
 class PIA {
 public:
-	PIA(): portb_cr(0), porta_cr(0) {}
-	virtual void reset() { portb_cr = porta_cr = 0; }
+	PIA(): portb(0), portb_cr(0), porta(0), porta_cr(0) {}
+	virtual void reset() { portb = portb_cr = porta = porta_cr = 0; }
 
 	void write(Memory::address, uint8_t);
 	uint8_t read(Memory::address);
@@ -14,37 +14,16 @@ public:
 	void restore(Stream &);
 
 protected:
-	// write to the "external" side of the port
-	void set_porta(uint8_t b) {
-		porta = b;
-		if (b & 0x80)
-			porta_cr = 0xa7;
-	}
-
 	// "device-side" operations (called from memory interface)
-	uint8_t read_porta() { return porta; }
-	virtual uint8_t read_porta_cr() {
-		if (porta_cr & 0x80) {
-			porta_cr = 0;
-			return 0xa7;
-		}
-		return porta_cr;
-	}
-	uint8_t read_portb() { return portb; }
-	uint8_t read_portb_cr() { return portb_cr; }
+	virtual uint8_t read_porta() { return porta; }
+	virtual uint8_t read_porta_cr() { return porta_cr; }
+	virtual uint8_t read_portb() { return portb; }
+	virtual uint8_t read_portb_cr() { return portb_cr; }
 
-	void write_porta(uint8_t b) { porta = b; }
-	void write_porta_cr(uint8_t b) {
-		if (!(porta_cr & 0x80) && b >= 0x80)
-			porta_cr |= 0x80;
-		else
-			porta_cr = b;
-	}
+	virtual void write_porta(uint8_t b) { porta = b; }
+	virtual void write_porta_cr(uint8_t b) { porta_cr = b; }
 	virtual void write_portb(uint8_t b) { portb = b; }
-	void write_portb_cr(uint8_t b) {
-		if (portb_cr < 0x80)
-			portb_cr = b;
-	}
+	virtual void write_portb_cr(uint8_t b) { portb_cr = b; }
 
 private:
 	uint8_t portb_cr, portb, porta_cr, porta;