From 734541ee05000bad9e9dd2f903a2db754e8c36f3 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Wed, 30 Aug 2023 20:49:39 +0200
Subject: [PATCH] Serial: Optimize SER_GET

There is no need to TryToSend before getting the character. We
send bytes during SER_PUT, and if interrupted during sending, we
still try to do it at the beginning of the next SER_PUT.
---
 libsrc/apple2/ser/a2.ssc.s      | 7 +------
 libsrc/atmos/ser/atmos-acia.s   | 8 +-------
 libsrc/c128/ser/c128-swlink.s   | 7 +------
 libsrc/c64/ser/c64-swlink.s     | 7 +------
 libsrc/cbm510/ser/cbm510-std.s  | 7 +------
 libsrc/cbm610/ser/cbm610-std.s  | 7 +------
 libsrc/plus4/ser/plus4-stdser.s | 7 +------
 7 files changed, 7 insertions(+), 43 deletions(-)

diff --git a/libsrc/apple2/ser/a2.ssc.s b/libsrc/apple2/ser/a2.ssc.s
index 12e975965..5942d43e9 100644
--- a/libsrc/apple2/ser/a2.ssc.s
+++ b/libsrc/apple2/ser/a2.ssc.s
@@ -291,14 +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
diff --git a/libsrc/atmos/ser/atmos-acia.s b/libsrc/atmos/ser/atmos-acia.s
index c918fe995..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
diff --git a/libsrc/c128/ser/c128-swlink.s b/libsrc/c128/ser/c128-swlink.s
index a0fc43050..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
diff --git a/libsrc/c64/ser/c64-swlink.s b/libsrc/c64/ser/c64-swlink.s
index c2934e669..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
diff --git a/libsrc/cbm510/ser/cbm510-std.s b/libsrc/cbm510/ser/cbm510-std.s
index 633a392c7..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
diff --git a/libsrc/cbm610/ser/cbm610-std.s b/libsrc/cbm610/ser/cbm610-std.s
index 1216e3794..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
diff --git a/libsrc/plus4/ser/plus4-stdser.s b/libsrc/plus4/ser/plus4-stdser.s
index d1d84267f..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