Files
open-roms/c64/kernal/tape/tape_common_prepare_cia.s
T
FeralChild64 d489e7bf41 tape routines can now be placed in Mega65 extra ROM space
commit 2f27e29758da1f1ec965588c0712125051a6f71a
Merge: ba722b1 796b62f
Author: FeralChild64 <you@example.com>
Date:   Tue Jan 28 17:34:53 2020 +0100

    Merge branch 'master' into tape_redirect

commit ba722b17e627af7dd067932688de0a3d86423e37
Author: FeralChild64 <you@example.com>
Date:   Tue Jan 28 17:28:19 2020 +0100

    finished Mega65 variant of tape routines

commit 47de685f2e08576504c5e00a5b7cb78498d22e72
Author: FeralChild64 <you@example.com>
Date:   Mon Jan 27 23:06:45 2020 +0100

    compilation fix

commit c3641acec049a7a6b53c35795b1f9e2df212cec2
Author: FeralChild64 <you@example.com>
Date:   Mon Jan 27 22:53:30 2020 +0100

    dependencies fix

commit dfad7a30bde043fa077005624dde1de4b72573b6
Merge: e4b0ec9 e410bc0
Author: FeralChild64 <you@example.com>
Date:   Mon Jan 27 21:25:49 2020 +0100

    Merge branch 'master' into tape_redirect

commit e4b0ec9c85861bde2ce52e0828d3bf895a681e17
Author: FeralChild64 <you@example.com>
Date:   Sat Jan 25 22:25:20 2020 +0100

    initial attempt to move tape code to Mega65 extra ROM
2020-01-28 17:35:42 +01:00

61 lines
1.3 KiB
ArmAsm

// #LAYOUT# STD * #TAKE
// #LAYOUT# M65 KERNAL_1 #TAKE
// #LAYOUT# * * #IGNORE
//
// Prepare CIA timers for tape reading
//
//
// Checked under VICE, PAL, average of 256 pulses:
//
// normal - short - timer goes down to $A5
// normal - medium - timer goes down to $7D
// normal - long - timer goes down to $52
//
// turbo - short - timer goes down to $CD
// turbo - long - timer goes down to $B1
//
//
// Measurement subroutine: .A should contain timer value, $C000-$C002 zeroed
//
// clc
// adc $C001
// sta $C001
// bcc !+
// inc $C000
// !:
// inc $C002
// beq !+
// rts
// !:
// lda $C000
// .break // .A contains our average
// rts
//
#if CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO
tape_common_prepare_cia:
// Setup CIA #2 timers
ldx #$03 // set timer A to 4 ticks
stx CIA2_TIMALO // $DD04
ldx #$00
stx CIA2_TIMAHI // $DD05
stx CIA2_TIMBHI // $DD07
dex // puts $FF - for running timer B as long as possible
stx CIA2_TIMBLO // $DD06
// Let timer A run continuously
ldx #%00010001 // start timer, force latch reload
stx CIA2_CRA // $DD0E
rts
#endif