;
-; Marco van den Heuvel, 2018-04-23
+; 2018-04-23, Marco van den Heuvel
+; 2018-04-26, Greg King
;
; extern 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.
; */
; extern unsigned char get_c128_speed (void);
; * 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
_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
-