diff --git a/src/aliases/,aliases_ram_lowmem.s b/src/aliases/,aliases_ram_lowmem.s
index ef37b7ac..7d6d20dd 100644
--- a/src/aliases/,aliases_ram_lowmem.s
+++ b/src/aliases/,aliases_ram_lowmem.s
@@ -103,11 +103,7 @@
 	.label PTR1      = $9E  //          for tape support, counter of errorneous bytes
 	.label PTR2      = $9F  //          for tape support, counter for errorneous bytes correction
 	.label TIME      = $A0  // $A0-$A2  jiffy clock
-#if !CONFIG_IEC_JIFFYDOS && !CONFIG_IEC_DOLPHINDOS && !CONFIG_IEC_BURST_CIA1 && !CONFIG_IEC_BURST_CIA2 && !CONFIG_IEC_BURST_MEGA_65
-	.label TSFCNT    = $A3  //          temporary variable for tape and IEC, [!] our usage differs
-#else
-	.label IECPROTO  = $A3  //          -- WIP -- [!] 0 = normal, 1 = JiffyDOS, >= $80 for unknown
-#endif
+	.label IECPROTO  = $A3  //          [!] IEC or pseudo-IEC protocol, >= $80 for unknown; originally named TSFCNT
 	.label TBTCNT    = $A4  //          temporary variable for tape and IEC, [!] our usage probably differs in details
 	.label CNTDN     = $A5  //          -- NOT IMPLEMENTED --
 	.label BUFPNT    = $A6  //          -- NOT IMPLEMENTED --
@@ -290,6 +286,25 @@
 	//                 $3FC     $3FC-$3FF  -- UNUSED --          free for user software
 
 
+//
+// Definitions for extended IEC functionality
+//
+
+	.const IEC_NORMAL  = 0 // has to be 0, always!
+#if CONFIG_IEC_JIFFYDOS 
+	.const IEC_JIFFY   = 1 // has to be 1, always!
+#endif
+#if CONFIG_IEC_DOLPHINDOS
+	.const IEC_DOLPHIN = 2
+#endif
+#if CONFIG_IEC_BURST_CIA1 || CONFIG_IEC_BURST_CIA2 || ROM_LAYOUT_M65
+	.const IEC_BURST   = 3
+#endif
+#if ROM_LAYOUT_M65
+	.const IEC_ROMDOS  = 4
+#endif
+
+
 //
 // Definitions for tape functionality
 //
diff --git a/src/kernal/iec/iec_rx_byte.s b/src/kernal/iec/iec_rx_byte.s
index 9dd110df..17c326e7 100644
--- a/src/kernal/iec/iec_rx_byte.s
+++ b/src/kernal/iec/iec_rx_byte.s
@@ -17,7 +17,7 @@
 iec_rx_dispatch:
 
 	lda IECPROTO
-	cmp #$01
+	cmp #IEC_JIFFY
 	beq_16 jiffydos_rx_byte
 
 	// FALLTROUGH
@@ -54,7 +54,7 @@ iec_rx_byte:
 
 	// Check if DolphinDOS was detected
 	lda IECPROTO
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	bne iec_rx_no_dolphindos
 
 	// For DolphinDOS just fetch the byte from parallel port
diff --git a/src/kernal/iec/iec_tx_byte.s b/src/kernal/iec/iec_tx_byte.s
index 53295b0a..e34e6da3 100644
--- a/src/kernal/iec/iec_tx_byte.s
+++ b/src/kernal/iec/iec_tx_byte.s
@@ -19,7 +19,7 @@ iec_tx_dispatch:
 
 	php                                // preserve C flag for EOI indication
 	lda IECPROTO
-	cmp #$01
+	cmp #IEC_JIFFY
 	bne !+
 
 	plp
@@ -71,7 +71,7 @@ iec_tx_common:
 
 	// Check if DolphinDOS was detected
 	lda IECPROTO
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	bne iec_tx_no_dolphindos
 
 	// For DolphinDOS just push the byte to parallel port (set it to output first)
diff --git a/src/kernal/iec/load_iec.s b/src/kernal/iec/load_iec.s
index fdd75f85..c9778dd0 100644
--- a/src/kernal/iec/load_iec.s
+++ b/src/kernal/iec/load_iec.s
@@ -107,12 +107,12 @@ load_iec:
 	lda IECPROTO
 
 #if CONFIG_IEC_JIFFYDOS
-	cmp #$01
+	cmp #IEC_JIFFY
 	beq_16 jiffydos_load               // branch if JiffyDOS
 #endif
 
 #if CONFIG_IEC_DOLPHINDOS
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	beq_16 dolphindos_load             // branch if DolphinDOS
 #endif
 
diff --git a/src/kernal/iec_fast/dolphindos_detect.s b/src/kernal/iec_fast/dolphindos_detect.s
index 92a53649..6cd288a0 100644
--- a/src/kernal/iec_fast/dolphindos_detect.s
+++ b/src/kernal/iec_fast/dolphindos_detect.s
@@ -56,7 +56,7 @@ dolphindos_detect_success:
 
 	// Protocol detected
 
-	lda #$02
+	lda #IEC_DOLPHIN
 	sta IECPROTO
 
 	rts
diff --git a/src/kernal/iec_fast/dolphindos_load.s b/src/kernal/iec_fast/dolphindos_load.s
index f32a8502..93a4970c 100644
--- a/src/kernal/iec_fast/dolphindos_load.s
+++ b/src/kernal/iec_fast/dolphindos_load.s
@@ -76,7 +76,7 @@ dolphindos_load_loop:
 	jsr iec_update_EAL_by_Y
 
 	// Restore proper IECPROTO value
-	lda #$02
+	lda #IEC_DOLPHIN
 	sta IECPROTO
 
 	// End of load loop
diff --git a/src/kernal/iec_fast/jiffydos_detect.s b/src/kernal/iec_fast/jiffydos_detect.s
index 3488ee6b..095bac78 100644
--- a/src/kernal/iec_fast/jiffydos_detect.s
+++ b/src/kernal/iec_fast/jiffydos_detect.s
@@ -33,12 +33,12 @@ jiffydos_detect_loop:
 	lda IECPROTO
 	bpl jiffydos_detect_end            // no detection requested, preserve existing protocol
 
-	lda #$00                           // normal protocol
+	lda #IEC_NORMAL                    // normal protocol
 	beq jiffydos_store_proto           // branch always
 
 jiffydos_detected:
 	jsr iec_wait_for_data_release      // guessed from VICE logs
-	lda #$01                           // JiffyDOS protocol
+	lda #IEC_JIFFY                     // JiffyDOS protocol
 
 	// FALLTROUGH
 
diff --git a/src/kernal/iec_fast/jiffydos_load.s b/src/kernal/iec_fast/jiffydos_load.s
index f8487e42..11eb8995 100644
--- a/src/kernal/iec_fast/jiffydos_load.s
+++ b/src/kernal/iec_fast/jiffydos_load.s
@@ -145,7 +145,7 @@ jiffydos_load_end:
 	sta C3PO
 
 	// Restore proper IECPROTO value
-	lda #$01
+	lda #IEC_JIFFY
 	sta IECPROTO
 
 #if CONFIG_IEC_JIFFYDOS_BLANK
diff --git a/src/kernal/iec_fast/jiffydos_rx_byte.s b/src/kernal/iec_fast/jiffydos_rx_byte.s
index 01473045..e0166b3e 100644
--- a/src/kernal/iec_fast/jiffydos_rx_byte.s
+++ b/src/kernal/iec_fast/jiffydos_rx_byte.s
@@ -102,7 +102,7 @@ jiffydos_rx_byte_end:
 	sta C3PO
 
 	// Restore proper IECPROTO value
-	lda #$01
+	lda #IEC_JIFFY
 	sta IECPROTO
 
 	// Re-enable sprites
diff --git a/src/kernal/iec_fast/jiffydos_tx_byte.s b/src/kernal/iec_fast/jiffydos_tx_byte.s
index e3ddcd06..272d0d62 100644
--- a/src/kernal/iec_fast/jiffydos_tx_byte.s
+++ b/src/kernal/iec_fast/jiffydos_tx_byte.s
@@ -83,7 +83,7 @@ jiffydos_tx_byte_finalize:
 	sta CIA2_PRA
 
 	// Restore proper IECPROTO value
-	lda #$01
+	lda #IEC_JIFFY
 	sta IECPROTO
 
 	// Re-enable sprites and interrupts