Detect ZRESET polarity

1 files changed, 31 insertions, 9 deletions

diff --git a/avr/z80-if.c b/avr/z80-if.c
index 08d417b..e36b369 100644
--- a/avr/z80-if.c
+++ b/avr/z80-if.c
@@ -78,6 +78,7 @@
 #define BUSACK		6
 #define DDR_BUSACK	DDRD
 #define P_RST		PORTD
+#define PIN_RST		PIND
 #define DDR_RST		DDRD
 #define RST		5
 
@@ -106,6 +107,7 @@
 #define Z80_O_BUSREQ	SBIT(P_BUSREQ, 7)
 //#define Z80_O_NMI	SBIT(P_NMI, )
 #define Z80_O_RST	SBIT(P_RST, 5)
+#define Z80_I_RST	SBIT(PIN_RST, 5)
 #define Z80_I_BUSACK	SBIT(PIN_BUSACK, 6)
 //#define Z80_I_HALT	SBIT(P_HALT, )
 
@@ -137,6 +139,7 @@
 
 static zstate_t zstate;
 static volatile uint8_t timer;		/* used for bus timeout */
+static bool reset_polarity;
 
 /*---------------------------------------------------------*/
 /* 10Hz timer interrupt generated by OC4A                  */
@@ -197,12 +200,27 @@ static void z80_dbus_set_out(void)
 	DDR_DB = 0xff;
 }
 
+static void z80_reset_active(void)
+{
+	if (reset_polarity)
+		Z80_O_RST = 1;
+	else
+		Z80_O_RST = 0;
+}
+
+static void z80_reset_inactive(void)
+{
+	if (reset_polarity)
+		Z80_O_RST = 0;
+	else
+		Z80_O_RST = 1;
+}
 
 static void z80_reset_pulse(void)
 {
-	Z80_O_RST = 0;
+	z80_reset_active();
 	_delay_us(10);
-	Z80_O_RST = 1;
+	z80_reset_inactive();
 }
 
 
@@ -210,9 +228,9 @@ void z80_setup_bus(void)
 {
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
 
-		/* /ZRESET: Output and low */
+		/* /ZRESET: Input, no pullup */
+		DDR_RST &= ~_BV(RST);
 		Z80_O_RST = 0;
-		DDR_RST |= _BV(RST);
 
 		/* /BUSREQ: Output and high */
 		Z80_O_BUSREQ = 1;
@@ -232,6 +250,10 @@ void z80_setup_bus(void)
 			DDR_SS = (DDR_SS & ~_BV(WAIT)) | _BV(RUN) | _BV(STEP);
 		}
 
+		reset_polarity = Z80_I_RST;
+		z80_reset_active();
+		DDR_RST |= _BV(RST);
+
 		zstate = RESET;
 	}
 
@@ -322,7 +344,7 @@ zstate_t z80_bus_cmd(bus_cmd_t cmd)
 	case Reset:
 		z80_dbus_set_in();
 		z80_addrbus_set_in();
-		Z80_O_RST = 0;
+		z80_reset_active();
 		Z80_O_BUSREQ = 1;
 		zstate = RESET;
 		break;
@@ -331,7 +353,7 @@ zstate_t z80_bus_cmd(bus_cmd_t cmd)
 		switch (zstate) {
 		case RESET:
 			Z80_O_BUSREQ = 0;
-			Z80_O_RST = 1;
+			z80_reset_inactive();
 			timer = BUS_TO;
 			while (Z80_I_BUSACK == 1 && timer)
 				;
@@ -339,7 +361,7 @@ zstate_t z80_bus_cmd(bus_cmd_t cmd)
 				z80_addrbus_set_out();
 				zstate = RESET_AQRD;
 			} else {
-				Z80_O_RST = 0;
+				z80_reset_active();
 				Z80_O_BUSREQ = 1;
 			}
 			break;
@@ -367,7 +389,7 @@ zstate_t z80_bus_cmd(bus_cmd_t cmd)
 		case RESET_AQRD:
 			z80_dbus_set_in();
 			z80_addrbus_set_in();
-			Z80_O_RST = 0;
+			z80_reset_active();
 			Z80_O_BUSREQ = 1;
 			zstate = RESET;
 			break;
@@ -385,7 +407,7 @@ zstate_t z80_bus_cmd(bus_cmd_t cmd)
 	case Run:
 		switch (zstate) {
 		case RESET:
-			Z80_O_RST = 1;
+			z80_reset_inactive();
 			zstate = RUNNING;
 			break;