Merge pull request #631 from blackystardust/master

[cc65] / libsrc / c128 / acc_c128_speed.s

diff --git a/libsrc/c128/acc_c128_speed.s b/libsrc/c128/acc_c128_speed.s
old mode 100755 (executable)
new mode 100644 (file)
index 3f2017d..7994a52
--- a/libsrc/c128/acc_c128_speed.s
+++ b/libsrc/c128/acc_c128_speed.s
@@ -1,21 +1,22 @@
 ;
-; Marco van den Heuvel, 2018-04-23
+; 2018-04-23, Marco van den Heuvel
+; 2018-04-26, Greg King
 ;
 
 ; unsigned char __fastcall__ set_c128_speed (unsigned char speed);
 ;
-;/* Set the speed of the C128 8502 CPU, using SPEED_SLOW will switch to
+;/* Set the speed of the C128 8502 CPU; using SPEED_SLOW will switch to
 ; * 1 Mhz (slow) mode, SPEED_2X or SPEED_FAST will switch to 2Mhz (fast) mode.
 ; *
 ; * Note that any value higher or equal to SPEED_2X will switch to fast mode.
 ; *
-; * This function will return the actual speed the CPU is at after trying
-; * to set the requested speed, to my knowledge the switching should not fail.
+; * This function will return the actual speed the CPU is at, after trying
+; * to set the requested speed; to my knowledge, the switching should not fail.
 ; *
-; * For C64 programs a check for a C128 in C64 mode is needed, make sure you
+; * For C64 programs, a check for a C128 in C64 mode is needed; make sure you
 ; * use 'detect_c128();' before using.
 ; *
-; * For C128 programs no detect function call is needed.
+; * For C128 programs, no detect function call is needed.
 ; */
 
 ; unsigned char get_c128_speed (void);
@@ -26,10 +27,10 @@
 ; * SPEED_SLOW  : Slow mode
 ; * SPEED_2X    : Fast mode
 ; *
-; * For C64 programs a check for a C128 in C64 mode is needed, make sure you
+; * For C64 programs, a check for a C128 in C64 mode is needed; make sure you
 ; * use 'detect_c128();' before using.
 ; *
-; * For C128 programs no detect function call is needed.
+; * For C128 programs, no detect function call is needed.
 ; */
 
         .export         _set_c128_speed
@@ -39,18 +40,12 @@
 
 _set_c128_speed:
         cmp     #SPEED_2X
-        bcs     high_speed
-store_speed:
+        lda     #$00                    ; clear VIC-IIe test bit
+        rol     a                       ; carry flag is speed bit
         sta     C128_VICIIE_CLK
 
-        .byte   $2C              ; skip over the lda #$01
-high_speed:
-        lda     #$01
-        bne     store_speed
-
 _get_c128_speed:
         lda     C128_VICIIE_CLK
         and     #$01
-        ldx     #$00
+        ldx     #>$0000
         rts
-