Added an extra drive on the shugart bus (index 3) this drive is select with pin 6 on the floppy header

Author: Per Mårtensson

src/floppy.c

@@ -43,7 +43,7 @@ static struct unit {
     bool_t initialised;
     bool_t is_flippy;
     bool_t motor;
-} unit[3];
+} unit[4];
 
 static struct gw_delay delay_params;
 static const struct gw_delay factory_delay_params = {
@@ -197,6 +197,7 @@ static void drive_deselect(void)
         case 0: pin = 10; break;
         case 1: pin = 12; break;
         case 2: pin = 14; break;
+        case 3: pin =  6; break;
         }
         break;
     }
@@ -230,6 +231,7 @@ static uint8_t drive_select(uint8_t nr)
         case 0: pin = 10; break;
         case 1: pin = 12; break;
         case 2: pin = 14; break;
+        case 3: pin =  6; break;
         default: return ACK_BAD_UNIT;
         }
         break;
@@ -264,7 +266,7 @@ static uint8_t drive_motor(uint8_t nr, bool_t on)
         }
         break;
     case BUS_SHUGART:
-        if (nr >= 3)
+        if (nr >= 4)
             return ACK_BAD_UNIT;
         /* All shugart units share one motor line. Alias them all to unit 0. */
         nr = 0;
@@ -305,7 +307,7 @@ static uint8_t drive_get_info(int nr, struct gw_drive_info *d)
             return ACK_BAD_UNIT;
         break;
     case BUS_SHUGART:
-        if (nr >= 3)
+        if (nr >= 4)
             return ACK_BAD_UNIT;
         break;
     default: