improved tape adapter handling

CONFIG.md

@@ -167,7 +167,7 @@ Needs about 100 more bytes in KERNAL segment.
 
 ### `CONFIG_TAPE_NO_KEY_SENSE`
 
-Enable this option if you are using a tape interface adapter with some audio signal source connected. These adapters lack key sense functionality, so the computer is unable to tell whether Play got pressed or not - with this option ROM will assume Play got pressed after impulses start arriving from the tape.
+Enable this option if you are using a tape interface adapter with some audio signal source connected. These adapters lack key sense functionality, so the computer is unable to tell whether Play got pressed or not - this option changes the ROM behaviour, so that it can detect Play pressed when impulses start arriving from the tape.
 
 ### `CONFIG_TAPE_NO_MOTOR_CONTROL`
 

c64/kernal/tape/tape_common.s

@@ -61,20 +61,49 @@ tape_wait_play_loop:
 
 #else
 
+	// The ROM is configured for tape adapter without the key sense - but it is still
+	// possible, that regular Datasette or Tapuino is connected
+
+	lda CPU_R6510
+	and #$10
+	beq tape_wait_first_pulse          // branch if button reported pressed, most likely really no key sense
+
+	// We have key sense - perform regular waiting
+!:
+	jsr STOP
+	bcs tape_break_error
+
+	lda CPU_R6510
+	and #$10
+	beq !-
+
+tape_wait_first_pulse:
+
 	// We have no key sense - so just turn the motor on and wait for the first pulse
 
 	jsr tape_motor_on
 
-	lda #$10
 !:
+	jsr STOP
+	bcs tape_break_error
+
+	lda #$10
 	bit CIA1_ICR    // $DC0D
 	bne !-
 !:
+	jsr STOP
+	bcs tape_break_error
+	
+	lda #$10
 	bit CIA1_ICR    // $DC0D
 	beq !-
 
 #endif
 
+	// FALLTROUGH
+
+tape_wait_play_done:
+
 #if CONFIG_MB_MEGA_65
 
 	// Display confirmation
@@ -84,10 +113,6 @@ tape_wait_play_loop:
 
 #endif
 
-	// FALLTROUGH
-
-tape_wait_play_done:
-
 	// Prepare for reading
 
 	lda #$01