diff --git a/libsrc/apple2/ser/a2.ssc.s b/libsrc/apple2/ser/a2.ssc.s
index 6ad9c3825..5942d43e9 100644
--- a/libsrc/apple2/ser/a2.ssc.s
+++ b/libsrc/apple2/ser/a2.ssc.s
@@ -26,6 +26,7 @@
         .include        "ser-error.inc"
 
         .macpack        module
+        .macpack        cpu
 
 ; ------------------------------------------------------------------------
 ; Header. Includes jump table
@@ -57,9 +58,13 @@
 ;----------------------------------------------------------------------------
 ; I/O definitions
 
+.if (.cpu .bitand CPU_ISET_65C02)
+ACIA            = $C088
+.else
 Offset          = $8F           ; Move 6502 false read out of I/O to page $BF
-
 ACIA            = $C088-Offset
+.endif
+
 ACIA_DATA       = ACIA+0        ; Data register
 ACIA_STATUS     = ACIA+1        ; Status register
 ACIA_CMD        = ACIA+2        ; Command register
@@ -200,7 +205,9 @@ SER_OPEN:
         asl
         asl
         asl
+.if .not (.cpu .bitand CPU_ISET_65C02)
         adc     #Offset                 ; Assume carry to be clear
+.endif
         tax
 
         ; Check if the handshake setting is valid
@@ -284,14 +291,9 @@ InvBaud:lda     #SER_ERR_BAUD_UNAVAIL
 
 SER_GET:
         ldx     Index
-        ldy     SendFreeCnt     ; Send data if necessary
-        iny                     ; Y == $FF?
-        beq     :+
-        lda     #$00            ; TryHard = false
-        jsr     TryToSend
 
         ; Check for buffer empty
-:       lda     RecvFreeCnt     ; (25)
+        lda     RecvFreeCnt     ; (25)
         cmp     #$FF
         bne     :+
         lda     #SER_ERR_NO_DATA
@@ -315,7 +317,11 @@ SER_GET:
         inc     RecvHead
         inc     RecvFreeCnt
         ldx     #$00            ; (59)
+.if (.cpu .bitand CPU_ISET_65C02)
+        sta     (ptr1)
+.else
         sta     (ptr1,x)
+.endif
         txa                     ; Return code = 0
         rts
 
@@ -328,20 +334,21 @@ SER_PUT:
 
         ; Try to send
         ldy     SendFreeCnt
-        iny                     ; Y = $FF?
+        cpy     #$FF            ; Nothing to flush
         beq     :+
         pha
         lda     #$00            ; TryHard = false
         jsr     TryToSend
         pla
 
-        ; Put byte into send buffer & send
-:       ldy     SendFreeCnt
+        ; Reload SendFreeCnt after TryToSend
+        ldy     SendFreeCnt
         bne     :+
         lda     #SER_ERR_OVERFLOW
         ldx     #0 ; return value is char
         rts
 
+        ; Put byte into send buffer & send
 :       ldy     SendTail
         sta     SendBuf,y
         inc     SendTail
@@ -404,19 +411,19 @@ SER_IRQ:
         and     #$08
         beq     Done            ; Jump if no ACIA interrupt
         lda     ACIA_DATA,x     ; Get byte from ACIA
-        ldy     RecvFreeCnt     ; Check if we have free space left
+        ldx     RecvFreeCnt     ; Check if we have free space left
         beq     Flow            ; Jump if no space in receive buffer
         ldy     RecvTail        ; Load buffer pointer
         sta     RecvBuf,y       ; Store received byte in buffer
         inc     RecvTail        ; Increment buffer pointer
         dec     RecvFreeCnt     ; Decrement free space counter
-        ldy     RecvFreeCnt     ; Check for buffer space low
-        cpy     #33
+        cpx     #33             ; Check for buffer space low
         bcc     Flow            ; Assert flow control if buffer space low
         rts                     ; Interrupt handled (carry already set)
 
         ; Assert flow control if buffer space too low
-Flow:   lda     RtsOff
+Flow:   ldx     Index
+lda     RtsOff
         sta     ACIA_CMD,x
         sta     Stopped
         sec                     ; Interrupt handled
@@ -427,12 +434,13 @@ Done:   rts
 
 TryToSend:
         sta     tmp1            ; Remember tryHard flag
-Again:  lda     SendFreeCnt
+NextByte:
+        lda     SendFreeCnt
         cmp     #$FF
         beq     Quit            ; Bail out
 
         ; Check for flow stopped
-        lda     Stopped
+Again:  lda     Stopped
         bne     Quit            ; Bail out
 
         ; Check that ACIA is ready to send
@@ -449,4 +457,4 @@ Send:   ldy     SendHead
         sta     ACIA_DATA,x
         inc     SendHead
         inc     SendFreeCnt
-        jmp     Again
+        jmp     NextByte
diff --git a/libsrc/atmos/ser/atmos-acia.s b/libsrc/atmos/ser/atmos-acia.s
index f679125d1..1509803d2 100644
--- a/libsrc/atmos/ser/atmos-acia.s
+++ b/libsrc/atmos/ser/atmos-acia.s
@@ -227,14 +227,8 @@ InvBaud:lda     #<SER_ERR_BAUD_UNAVAIL
 ; returned.
 
 SER_GET:
-        ldy     SendFreeCnt     ; Send data if necessary
-        iny                     ; Y == $FF?
-        beq     :+
-        lda     #$00            ; TryHard = false
-        jsr     TryToSend
-
         ; Check for buffer empty
-:       lda     RecvFreeCnt     ; (25)
+        lda     RecvFreeCnt     ; (25)
         cmp     #$FF
         bne     :+
         lda     #SER_ERR_NO_DATA
@@ -269,20 +263,21 @@ SER_GET:
 SER_PUT:
         ; Try to send
         ldy     SendFreeCnt
-        iny                     ; Y = $FF?
+        cpy     #$FF            ; Nothing to flush
         beq     :+
         pha
         lda     #$00            ; TryHard = false
         jsr     TryToSend
         pla
 
-        ; Put byte into send buffer & send
-:       ldy     SendFreeCnt
+        ; Reload SendFreeCnt after TryToSend
+        ldy     SendFreeCnt
         bne     :+
         lda     #SER_ERR_OVERFLOW
         ldx     #0 ; return value is char
         rts
 
+        ; Put byte into send buffer & send
 :       ldy     SendTail
         sta     SendBuf,y
         inc     SendTail
@@ -329,19 +324,19 @@ SER_IRQ:
         and     #$08
         beq     Done            ; Jump if no ACIA interrupt
         lda     ACIA::DATA,x    ; Get byte from ACIA
-        ldy     RecvFreeCnt     ; Check if we have free space left
+        ldx     RecvFreeCnt     ; Check if we have free space left
         beq     Flow            ; Jump if no space in receive buffer
         ldy     RecvTail        ; Load buffer pointer
         sta     RecvBuf,y       ; Store received byte in buffer
         inc     RecvTail        ; Increment buffer pointer
         dec     RecvFreeCnt     ; Decrement free space counter
-        ldy     RecvFreeCnt     ; Check for buffer space low
-        cpy     #33
+        cpx     #33
         bcc     Flow            ; Assert flow control if buffer space low
         rts                     ; Interrupt handled (carry already set)
 
         ; Assert flow control if buffer space too low
-Flow:   lda     RtsOff
+Flow:   ldx     Index           ; Reload port
+        lda     RtsOff
         sta     ACIA::CMD,x
         sta     Stopped
         sec                     ; Interrupt handled
@@ -352,12 +347,13 @@ Done:   rts
 
 TryToSend:
         sta     tmp1            ; Remember tryHard flag
-Again:  lda     SendFreeCnt
+NextByte:
+        lda     SendFreeCnt
         cmp     #$FF
         beq     Quit            ; Bail out
 
         ; Check for flow stopped
-        lda     Stopped
+Again:  lda     Stopped
         bne     Quit            ; Bail out
 
         ; Check that ACIA is ready to send
@@ -374,4 +370,4 @@ Send:   ldy     SendHead
         sta     ACIA::DATA
         inc     SendHead
         inc     SendFreeCnt
-        jmp     Again
+        jmp     NextByte
diff --git a/libsrc/c128/ser/c128-swlink.s b/libsrc/c128/ser/c128-swlink.s
index 7d36eb5bc..b8f08159b 100644
--- a/libsrc/c128/ser/c128-swlink.s
+++ b/libsrc/c128/ser/c128-swlink.s
@@ -314,15 +314,10 @@ SER_CLOSE:
 ;
 
 SER_GET:
-        ldx     SendFreeCnt             ; Send data if necessary
-        inx                             ; X == $FF?
-        beq     @L1
-        lda     #$00
-        jsr     TryToSend
 
 ; Check for buffer empty
 
-@L1:    lda     RecvFreeCnt             ; (25)
+        lda     RecvFreeCnt             ; (25)
         cmp     #$ff
         bne     @L2
         lda     #SER_ERR_NO_DATA
@@ -362,21 +357,23 @@ SER_PUT:
 ; Try to send
 
         ldx     SendFreeCnt
-        inx                             ; X = $ff?
+        cpx     #$FF                   ; Nothing to flush
         beq     @L2
         pha
         lda     #$00
         jsr     TryToSend
         pla
 
-; Put byte into send buffer & send
+; Reload SendFreeCnt after TryToSend
 
-@L2:    ldx     SendFreeCnt
-        bne     @L3
+        ldx     SendFreeCnt
+        bne     @L2
         lda     #SER_ERR_OVERFLOW       ; X is already zero
         rts
 
-@L3:    ldx     SendTail
+; Put byte into send buffer & send
+
+@L2:    ldx     SendTail
         sta     SendBuf,x
         inc     SendTail
         dec     SendFreeCnt
@@ -466,25 +463,25 @@ NmiHandler:
         sta     tmp1            ; Remember tryHard flag
 @L0:    lda     SendFreeCnt
         cmp     #$ff
-        beq     @L3             ; Bail out
+        beq     @L2             ; Bail out
 
 ; Check for flow stopped
 
 @L1:    lda     Stopped
-        bne     @L3             ; Bail out
+        bne     @L2             ; Bail out
 
 ; Check that swiftlink is ready to send
 
-@L2:    lda     ACIA_STATUS
+        lda     ACIA_STATUS
         and     #$10
-        bne     @L4
+        bne     @L3
         bit     tmp1            ;keep trying if must try hard
-        bmi     @L0
-@L3:    rts
+        bmi     @L1
+@L2:    rts
 
 ; Send byte and try again
 
-@L4:    ldx     SendHead
+@L3:    ldx     SendHead
         lda     SendBuf,x
         sta     ACIA_DATA
         inc     SendHead
diff --git a/libsrc/c64/ser/c64-swlink.s b/libsrc/c64/ser/c64-swlink.s
index 81c9916a6..067a7ca92 100644
--- a/libsrc/c64/ser/c64-swlink.s
+++ b/libsrc/c64/ser/c64-swlink.s
@@ -288,15 +288,10 @@ SER_CLOSE:
 ;
 
 SER_GET:
-        ldx     SendFreeCnt             ; Send data if necessary
-        inx                             ; X == $FF?
-        beq     @L1
-        lda     #$00
-        jsr     TryToSend
 
 ; Check for buffer empty
 
-@L1:    lda     RecvFreeCnt             ; (25)
+        lda     RecvFreeCnt             ; (25)
         cmp     #$ff
         bne     @L2
         lda     #SER_ERR_NO_DATA
@@ -336,21 +331,23 @@ SER_PUT:
 ; Try to send
 
         ldx     SendFreeCnt
-        inx                             ; X = $ff?
+        cpx     #$FF                   ; Nothing to flush
         beq     @L2
         pha
         lda     #$00
         jsr     TryToSend
         pla
 
-; Put byte into send buffer & send
+; Reload SendFreeCnt after TryToSend
 
-@L2:    ldx     SendFreeCnt
-        bne     @L3
+        ldx     SendFreeCnt
+        bne     @L2
         lda     #SER_ERR_OVERFLOW      ; X is already zero
         rts
 
-@L3:    ldx     SendTail
+; Put byte into send buffer & send
+
+@L2:    ldx     SendTail
         sta     SendBuf,x
         inc     SendTail
         dec     SendFreeCnt
@@ -443,25 +440,25 @@ NmiHandler:
         sta     tmp1            ; Remember tryHard flag
 @L0:    lda     SendFreeCnt
         cmp     #$ff
-        beq     @L3             ; Bail out
+        beq     @L2             ; Bail out
 
 ; Check for flow stopped
 
 @L1:    lda     Stopped
-        bne     @L3             ; Bail out
+        bne     @L2             ; Bail out
 
 ; Check that swiftlink is ready to send
 
-@L2:    lda     ACIA_STATUS
+        lda     ACIA_STATUS
         and     #$10
-        bne     @L4
+        bne     @L3
         bit     tmp1            ;keep trying if must try hard
-        bmi     @L0
-@L3:    rts
+        bmi     @L1
+@L2:    rts
 
 ; Send byte and try again
 
-@L4:    ldx     SendHead
+@L3:    ldx     SendHead
         lda     SendBuf,x
         sta     ACIA_DATA
         inc     SendHead
diff --git a/libsrc/cbm510/ser/cbm510-std.s b/libsrc/cbm510/ser/cbm510-std.s
index cc58c1233..800007492 100644
--- a/libsrc/cbm510/ser/cbm510-std.s
+++ b/libsrc/cbm510/ser/cbm510-std.s
@@ -244,15 +244,10 @@ InvBaud:
 ;
 
 SER_GET:
-        ldx     SendFreeCnt             ; Send data if necessary
-        inx                             ; X == $FF?
-        beq     @L1
-        lda     #$00
-        jsr     TryToSend
 
 ; Check for buffer empty
 
-@L1:    lda     RecvFreeCnt
+        lda     RecvFreeCnt
         cmp     #$ff
         bne     @L2
         lda     #SER_ERR_NO_DATA
@@ -292,21 +287,23 @@ SER_PUT:
 ; Try to send
 
         ldx     SendFreeCnt
-        inx                             ; X = $ff?
+        cpx     #$FF                   ; Nothing to flush
         beq     @L2
         pha
         lda     #$00
         jsr     TryToSend
         pla
 
-; Put byte into send buffer & send
+; Reload SendFreeCnt after TryToSend
 
-@L2:    ldx     SendFreeCnt
-        bne     @L3
+        ldx     SendFreeCnt
+        bne     @L2
         lda     #SER_ERR_OVERFLOW      ; X is already zero
         rts
 
-@L3:    ldx     SendTail
+; Put byte into send buffer & send
+
+@L2:    ldx     SendTail
         sta     SendBuf,x
         inc     SendTail
         dec     SendFreeCnt
@@ -395,31 +392,31 @@ SER_IRQ:
         sta     IndReg          ; Switch to the system bank
 @L0:    lda     SendFreeCnt
         cmp     #$ff
-        beq     @L3             ; Bail out
+        beq     @L2             ; Bail out
 
 ; Check for flow stopped
 
 @L1:    lda     Stopped
-        bne     @L3             ; Bail out
+        bne     @L2             ; Bail out
 
 ; Check that swiftlink is ready to send
 
-@L2:    ldy     #ACIA::STATUS
+        ldy     #ACIA::STATUS
         lda     (acia),y
         and     #$10
-        bne     @L4
+        bne     @L3
         bit     tmp1            ; Keep trying if must try hard
-        bmi     @L0
+        bmi     @L1
 
 ; Switch back the bank and return
 
-@L3:    lda     ExecReg
+@L2:    lda     ExecReg
         sta     IndReg
         rts
 
 ; Send byte and try again
 
-@L4:    ldx     SendHead
+@L3:    ldx     SendHead
         lda     SendBuf,x
         ldy     #ACIA::DATA
         sta     (acia),y
diff --git a/libsrc/cbm610/ser/cbm610-std.s b/libsrc/cbm610/ser/cbm610-std.s
index f7ddde935..45b18eadf 100644
--- a/libsrc/cbm610/ser/cbm610-std.s
+++ b/libsrc/cbm610/ser/cbm610-std.s
@@ -245,15 +245,10 @@ InvBaud:
 ;
 
 SER_GET:
-        ldx     SendFreeCnt             ; Send data if necessary
-        inx                             ; X == $FF?
-        beq     @L1
-        lda     #$00
-        jsr     TryToSend
 
 ; Check for buffer empty
 
-@L1:    lda     RecvFreeCnt
+        lda     RecvFreeCnt
         cmp     #$ff
         bne     @L2
         lda     #SER_ERR_NO_DATA
@@ -293,21 +288,23 @@ SER_PUT:
 ; Try to send
 
         ldx     SendFreeCnt
-        inx                             ; X = $ff?
+        cpx     #$ff                   ; Nothing to flush
         beq     @L2
         pha
         lda     #$00
         jsr     TryToSend
         pla
 
-; Put byte into send buffer & send
+; Reload SendFreeCnt after TryToSend
 
-@L2:    ldx     SendFreeCnt
-        bne     @L3
+        ldx     SendFreeCnt
+        bne     @L2
         lda     #SER_ERR_OVERFLOW      ; X is already zero
         rts
 
-@L3:    ldx     SendTail
+; Put byte into send buffer & send
+
+@L2:    ldx     SendTail
         sta     SendBuf,x
         inc     SendTail
         dec     SendFreeCnt
@@ -395,31 +392,31 @@ SER_IRQ:
         sta     IndReg          ; Switch to the system bank
 @L0:    lda     SendFreeCnt
         cmp     #$ff
-        beq     @L3             ; Bail out
+        beq     @L2             ; Bail out
 
 ; Check for flow stopped
 
 @L1:    lda     Stopped
-        bne     @L3             ; Bail out
+        bne     @L2             ; Bail out
 
 ; Check that swiftlink is ready to send
 
-@L2:    ldy     #ACIA::STATUS
+       ldy     #ACIA::STATUS
         lda     (acia),y
         and     #$10
-        bne     @L4
+        bne     @L3
         bit     tmp1            ; Keep trying if must try hard
-        bmi     @L0
+        bmi     @L1
 
 ; Switch back the bank and return
 
-@L3:    lda     ExecReg
+@L2:    lda     ExecReg
         sta     IndReg
         rts
 
 ; Send byte and try again
 
-@L4:    ldx     SendHead
+@L3:    ldx     SendHead
         lda     SendBuf,x
         ldy     #ACIA::DATA
         sta     (acia),y
diff --git a/libsrc/plus4/ser/plus4-stdser.s b/libsrc/plus4/ser/plus4-stdser.s
index fbdc61b2e..77445c7a2 100644
--- a/libsrc/plus4/ser/plus4-stdser.s
+++ b/libsrc/plus4/ser/plus4-stdser.s
@@ -252,15 +252,10 @@ InvBaud:
 ;
 
 SER_GET:
-        ldx     SendFreeCnt             ; Send data if necessary
-        inx                             ; X == $FF?
-        beq     @L1
-        lda     #$00
-        jsr     TryToSend
 
 ; Check for buffer empty
 
-@L1:    lda     RecvFreeCnt             ; (25)
+        lda     RecvFreeCnt             ; (25)
         cmp     #$ff
         bne     @L2
         lda     #SER_ERR_NO_DATA
@@ -300,21 +295,23 @@ SER_PUT:
 ; Try to send
 
         ldx     SendFreeCnt
-        inx                             ; X = $ff?
+        cpx     #$ff                   ; Nothing to flush
         beq     @L2
         pha
         lda     #$00
         jsr     TryToSend
         pla
 
-; Put byte into send buffer & send
+; Reload SendFreeCnt after TryToSend
 
-@L2:    ldx     SendFreeCnt
-        bne     @L3
+        ldx     SendFreeCnt
+        bne     @L2
         lda     #SER_ERR_OVERFLOW      ; X is already zero
         rts
 
-@L3:    ldx     SendTail
+; Put byte into send buffer & send
+
+@L2:    ldx     SendTail
         sta     SendBuf,x
         inc     SendTail
         dec     SendFreeCnt
@@ -387,25 +384,25 @@ SER_IRQ:
         sta     tmp1            ; Remember tryHard flag
 @L0:    lda     SendFreeCnt
         cmp     #$ff
-        beq     @L3             ; Bail out
+        beq     @L2             ; Bail out
 
 ; Check for flow stopped
 
 @L1:    lda     Stopped
-        bne     @L3             ; Bail out
+        bne     @L2             ; Bail out
 
 ; Check that swiftlink is ready to send
 
-@L2:    lda     ACIA_STATUS
+        lda     ACIA_STATUS
         and     #$10
-        bne     @L4
+        bne     @L3
         bit     tmp1            ;keep trying if must try hard
-        bmi     @L0
-@L3:    rts
+        bmi     @L1
+@L2:    rts
 
 ; Send byte and try again
 
-@L4:    ldx     SendHead
+@L3:    ldx     SendHead
         lda     SendBuf,x
         sta     ACIA_DATA
         inc     SendHead