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57 lines
1.5 KiB
ArmAsm
57 lines
1.5 KiB
ArmAsm
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; Marco van den Heuvel, 2018-04-23
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;
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; extern unsigned char __fastcall__ set_c128_speed (unsigned char speed);
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;
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;/* Set the speed of the C128 8502 CPU, using SPEED_SLOW will switch to
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; * 1 Mhz (slow) mode, SPEED_2X or SPEED_FAST will switch to 2Mhz (fast) mode.
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; *
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; * Note that any value higher or equal to SPEED_2X will switch to fast mode.
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; *
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; * This function will return the actual speed the CPU is at after trying
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; * to set the requested speed, to my knowledge the switching should not fail.
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; *
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; * For C64 programs a check for a C128 in C64 mode is needed, make sure you
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; * use 'detect_c128();' before using.
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; *
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; * For C128 programs no detect function call is needed.
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; */
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; extern unsigned char get_c128_speed (void);
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;
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;/* Get the speed of the C128 8502 CPU.
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; *
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; * Possible return values:
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; * SPEED_SLOW : Slow mode
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; * SPEED_2X : Fast mode
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; *
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; * For C64 programs a check for a C128 in C64 mode is needed, make sure you
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; * use 'detect_c128();' before using.
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; *
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; * For C128 programs no detect function call is needed.
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; */
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.export _set_c128_speed
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.export _get_c128_speed
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.include "accelerator.inc"
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_set_c128_speed:
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cmp #SPEED_2X
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bcs high_speed
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store_speed:
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sta C128_VICIIE_CLK
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.byte $2C ; skip over the lda #$01
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high_speed:
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lda #$01
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bne store_speed
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_get_c128_speed:
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lda C128_VICIIE_CLK
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and #$01
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ldx #$00
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rts
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